[binutils-gdb] Document that the PATTERN argument to gdb_test is optional.

[sergiodj+buildbot@redhat.com]

*** TEST RESULTS FOR COMMIT 79fad5b803e22798bcb087066234a954d0ccdc60 ***

Author: Sandra Loosemore <sandra@codesourcery.com>
Branch: master
Commit: 79fad5b803e22798bcb087066234a954d0ccdc60

Document that the PATTERN argument to gdb_test is optional.

2015-12-25  Sandra Loosemore  <sandra@codesourcery.com>

	gdb/testsuite/
	* lib/gdb.exp (gdb_test): Update comments to clarify that the
	PATTERN argument is optional.