Don't consider changes to basic types as being redundant

Don't consider changes to basic types as being redundant

Suppose we have two types struct A and struct B.  Suppose the two
types have members of integer type.  Suppose there are members of
integer type in struct A that are modified to become members of char
type.  Suppose, at last, that we also have members of integer type in
struct B that are modified to become members of char type.

In that case, we want to see all the changes of members which types
got changed from integer type to char type.  None of these changes
should be considered redundant.

Today, unfortunately, only the first change is reported by default.
The subsequent changes are considered to be redundant.

This patch fixes that by considering that changes that modifies the type of a
decl from a basic type into another are never considered redundant.

	* include/abg-comparison.h (is_diff_of_basic_type)
	(has_basic_type_change_only): Declare these functions ...
	* src/abg-comparison.cc (is_diff_of_basic_type)
	(has_basic_type_change_only): ... and define them.
	(redundancy_marking_visitor::visit_begin): Use the new
	has_basic_type_change_only.
	* tests/data/test-diff-filter/libtest37-v0.so: New binary test input.
	* tests/data/test-diff-filter/libtest37-v1.so: Likewise.
	* tests/data/test-diff-filter/test37-report-0.txt: New test
	reference output.
	* tests/data/test-diff-filter/test37-v0.cc: Source code of the new
	binary test input.
	* tests/data/test-diff-filter/test37-v1.cc: Likewise.
	* tests/data/Makefile.am: Update to add the new test material to
	the source distribution.
	* tests/test-diff-filter.cc (in_out_spec): Add the new test input
	to this test harness.

Signed-off-by: Dodji Seketeli <dodji@redhat.com>