[binutils-gdb] Make copy_token_string return unique_xmalloc_ptr

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT a5b5adf529fa64391bc1ef733b3e78f15d94c4b9 ***

Author: Tom Tromey <tom@tromey.com>
Branch: master
Commit: a5b5adf529fa64391bc1ef733b3e78f15d94c4b9

Make copy_token_string return unique_xmalloc_ptr

This changes copy_token_string to return a unique_xmalloc_ptr, which
allows the removal of some cleanups.

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

	* linespec.c (copy_token_string): Return a unique_xmalloc_ptr.
	(unexpected_linespec_error): Update.
	(linespec_parse_basic, parse_linespec): Update.