[binutils-gdb] Remove cleanup from old_renaming_is_invisible

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 49d83361cda4614f571f46c6bc0464092daf3dc9 ***

Author: Tom Tromey <tom@tromey.com>
Branch: master
Commit: 49d83361cda4614f571f46c6bc0464092daf3dc9

Remove cleanup from old_renaming_is_invisible

This removes a cleanup from ada-lang.c by changing xget_renaming_scope
to return a std::string.

ChangeLog
2018-05-04  Tom Tromey  <tom@tromey.com>

	* ada-lang.c (xget_renaming_scope): Return std::string.
	(old_renaming_is_invisible): Update.