[binutils-gdb] Use gdbpy_ref in gdbpy_string_to_argv

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT d1b3de2e43380a0c51772a40315cd2268573d985 ***

Author: Tom Tromey <tom@tromey.com>
Branch: master
Commit: d1b3de2e43380a0c51772a40315cd2268573d985

Use gdbpy_ref in gdbpy_string_to_argv

This chanes gdbpy_string_to_argv to use gdbpy_ref.

2017-01-10  Tom Tromey  <tom@tromey.com>

	* python/py-cmd.c (gdbpy_string_to_argv): Use gdbpy_ref.