Remove cleanups from findcmd.c

Remove cleanups from findcmd.c

This removes cleanups from findcmd.c, replacing manual buffer
management with a gdb::byte_vector.

ChangeLog
2017-09-11  Tom Tromey  <tom@tromey.com>

	* findcmd.c (put_bits): Take a gdb::byte_vector.
	(parse_find_args): Return gdb::byte_vector.  "args" now const.
	Remove "pattern_bufp" and "pattern_lenp" parameters.  Remove
	cleanups.
	(find_command): Update.