replace convert_ascii_to_int with hex2bin

replace convert_ascii_to_int with hex2bin

convert_ascii_to_int is identical to hex2bin.
This removes the former.

2014-02-12  Tom Tromey  <tromey@redhat.com>

	* common/rsp-low.c (convert_ascii_to_int): Remove.
	* common/rsp-low.h (convert_ascii_to_int): Don't declare.

2014-02-12  Tom Tromey  <tromey@redhat.com>

	* ax.c (gdb_parse_agent_expr): Use hex2bin, not
	convert_ascii_to_int.
	* regcache.c (registers_to_string): Likewise.
	* remote-utils.c (decode_M_packet): Likewise.
	* server.c (process_serial_event): Likewise.