Garbage collect py-utils.c:target_string_to_unicode.

Garbage collect py-utils.c:target_string_to_unicode.

The strlen in this function looked suspicious, for the function
documents that STR is in the target's charset (what if it is utf-32,
etc.).

On closer inspection, nothing is calling the function, and it's been
that way ever since the function was added.

gdb/
2013-03-06  Pedro Alves  <palves@redhat.com>

	* python/py-utils.c (target_string_to_unicode): Delete function.
	* python/python-internal.h (target_string_to_unicode): Delete
	declaration.