Don't ignore options when diffing translation units (.bi files).

Don't ignore options when diffing translation units (.bi files).

There was an inconsistency in the way the diff context was used for
different file types. This change eliminates this and so .bi files now
have all the command line options applied to their diffs.

	* tests/data/Makefile.am: Add test case files.
	* tests/data/test-abidiff-exit/test-loc-*: New test cases.
	* tests/test-abidiff-exit.cc (in_out_specs): Add new test cases.
	* tools/abidiff.cc (main): Use populated ctxt for translation unit
	diff.

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