[binutils-gdb] Make read_program_header return a gdb::byte_vector

[sergiodj+buildbot at sergiodj dot net]

*** TEST RESULTS FOR COMMIT 17658d46e48ad4a7f6fb850422639b06c9d963aa ***

Author: Simon Marchi <simon.marchi@polymtl.ca>
Branch: master
Commit: 17658d46e48ad4a7f6fb850422639b06c9d963aa

Make read_program_header return a gdb::byte_vector

While reading a recent patch, I found this spot where a gdb::byte_vector
could be used instead of an allocated buffer returned as a plain
pointer.

gdb/ChangeLog:

	* solib-svr4.c (read_program_header): Return
	gdb::optional<gdb::byte_vector>, remove p_sect_size param.
	(find_program_interpreter): Return
	gdb::optional<gdb::byte_vector>.
	(scan_dyntag_auxv): Adjust.
	(enable_break): Adjust.
	(svr4_exec_displacement): Adjust.