abg-writer.cc: Clean up new line emission.

abg-writer.cc: Clean up new line emission.

The XML writer has a few different styles of new line handling in
different places. Some functions are responsible for line termination,
others are not and there is bespoke logic and state variables in a few
places.

Extra or missing newlines should have no impact on the semantics of
any given ABI file but they do affect textual diffs and diff
statistics.

By insisting the XML emitted should have exactly one XML tag (or
comment) per line, we can simplify the code and make it more
composable.

This commit does this, yielding a modest reduction in code size and
eliminating all blank lines in XML output (7127 blank lines in current
tests). The commit also fixes some code whitespace.

	* src/abg-writer.cc (annotate): In the
	function_decl::parameter_sptr overload, fix code whitespace.
	(write_decl_in_scope): Remove wrote_context state variable and
	associated logic; emit new line unconditionally after end of
	XML tags and nowhere else.
	(write_canonical_types_of_scope): Emit new line after end of
	XML comment and nowhere else.
	(write_translation_unit): Emit new line after end of XML tags
	and nowhere else.
	(write_type_decl): Likewise.
	(write_namespace_decl): Likewise.
	(write_qualified_type_def): Emit new line after end of XML tag.
	(write_pointer_type_def): Likewise.
	(write_reference_type_def): Likewise.
	(write_array_type_def): Emit new line after end of XML tags
	and nowhere else.
	(write_enum_type_decl): Emit new line after end of XML tag.
	(write_elf_symbol): Likewise.
	(write_elf_symbols_table): Emit no new lines.
	(write_elf_needed): Emit new line unconditionally after end of
	XML tags.
	(write_typedef_decl): Emit new line after end of XML tag.
	(write_var_decl): Emit new line after end of XML tag.
	(write_function_decl): Likewise.
	(write_function_type): Fold two output statements into
	one; emit new line after end of XML tag.
	(write_class_decl_opening_tag): Emit new line unconditionally
	after end of XML tags and simplify empty element tag logic.
	(write_union_decl_opening_tag): Likewise.
	(write_class_decl): Emit new line after end of XML tag and
	nowhere else.
	(write_union_decl): Likewise.
	(write_member_type_opening_tag): Emit new line after end of
	XML tag.
	(write_member_type): Emit new lines only after XML tags.
	(write_type_tparameter): Emit new line after XML tag.
	(write_non_type_tparameter): Likewise.
	(write_template_tparameter): Emit new line after XML tag and
	nowhere else.
	(write_type_composition): Likewise.
	(write_template_parameters): Emit no new lines.
	(write_function_tdecl): Emit new line after XML tag and
	nowhere else.
	(write_class_tdecl): Likewise.
	(write_corpus): Emit new lines only after XML tags.
	(dump): In the decl_base_sptr overload, don't emit final new
	line as this is now done by write_decl. In the var_decl_sptr
	overload, don't emit final new line (mistakenly done to cerr
	instead of o) as this is now done by write_var_decl. In the
	translation_unit overload, don't emit final new line as this
	doubles that emitted by write_translation_unit.
	* tests/data/test-annotate/libtest23.so.abi: Delete all blank
	lines.
	* tests/data/test-annotate/libtest24-drop-fns-2.so.abi: Ditto.
	* tests/data/test-annotate/libtest24-drop-fns.so.abi: Ditto.
	* tests/data/test-annotate/test-anonymous-members-0.o.abi:
	Ditto.
	* tests/data/test-annotate/test1.abi: Ditto.
	* tests/data/test-annotate/test13-pr18894.so.abi: Ditto.
	* tests/data/test-annotate/test14-pr18893.so.abi: Ditto.
	* tests/data/test-annotate/test15-pr18892.so.abi: Ditto.
	* tests/data/test-annotate/test17-pr19027.so.abi: Ditto.
	* tests/data/test-annotate/test18-pr19037-libvtkRenderingLIC-6.1.so.abi:
	Ditto.
	* tests/data/test-annotate/test19-pr19023-libtcmalloc_and_profiler.so.abi:
	Ditto.
	* tests/data/test-annotate/test20-pr19025-libvtkParallelCore-6.1.so.abi:
	Ditto.
	* tests/data/test-annotate/test21-pr19092.so.abi: Ditto.
	* tests/data/test-annotate/test7.so.abi: Ditto.
	* tests/data/test-read-dwarf/PR22015-libboost_iostreams.so.abi:
	Ditto.
	* tests/data/test-read-dwarf/PR22122-libftdc.so.abi: Ditto.
	* tests/data/test-read-dwarf/PR25007-sdhci.ko.abi: Ditto.
	* tests/data/test-read-dwarf/PR25042-libgdbm-clang-dwarf5.so.6.0.0.abi:
	Ditto.
	* tests/data/test-read-dwarf/libtest23.so.abi: Ditto.
	* tests/data/test-read-dwarf/libtest24-drop-fns-2.so.abi:
	Ditto.
	* tests/data/test-read-dwarf/libtest24-drop-fns.so.abi: Ditto.
	* tests/data/test-read-dwarf/test1.abi: Ditto.
	* tests/data/test-read-dwarf/test1.hash.abi: Ditto.
	* tests/data/test-read-dwarf/test10-pr18818-gcc.so.abi: Ditto.
	* tests/data/test-read-dwarf/test11-pr18828.so.abi: Ditto.
	* tests/data/test-read-dwarf/test12-pr18844.so.abi: Ditto.
	* tests/data/test-read-dwarf/test13-pr18894.so.abi: Ditto.
	* tests/data/test-read-dwarf/test14-pr18893.so.abi: Ditto.
	* tests/data/test-read-dwarf/test15-pr18892.so.abi: Ditto.
	* tests/data/test-read-dwarf/test16-pr18904.so.abi: Ditto.
	* tests/data/test-read-dwarf/test17-pr19027.so.abi: Ditto.
	* tests/data/test-read-dwarf/test18-pr19037-libvtkRenderingLIC-6.1.so.abi:
	Ditto.
	* tests/data/test-read-dwarf/test19-pr19023-libtcmalloc_and_profiler.so.abi:
	Ditto.
	* tests/data/test-read-dwarf/test20-pr19025-libvtkParallelCore-6.1.so.abi:
	Ditto.
	* tests/data/test-read-dwarf/test21-pr19092.so.abi: Ditto.
	* tests/data/test-read-dwarf/test22-pr19097-libstdc++.so.6.0.17.so.abi:
	Ditto.
	* tests/data/test-read-dwarf/test7.so.abi: Ditto.
	* tests/data/test-read-dwarf/test7.so.hash.abi: Ditto.
	* tests/data/test-read-dwarf/test9-pr18818-clang.so.abi:
	Ditto.
	* tests/data/test-read-write/test10.xml: Ditto.
	* tests/data/test-read-write/test15.xml: Ditto.
	* tests/data/test-read-write/test21.xml: Ditto.
	* tests/data/test-read-write/test25.xml: Ditto.
	* tests/data/test-read-write/test28-without-std-fns-ref.xml:
	Ditto.
	* tests/data/test-read-write/test28-without-std-vars-ref.xml:
	Ditto.

Signed-off-by: Giuliano Procida <gprocida@google.com>
Signed-off-by: Dodji Seketeli <dodji@redhat.com>