Use rs->buf after getpkt

Hi,
The following code snippet looks wrong to me

 char *buf = rs->buf;

 getpkt (&rs->buf, &rs->buf_size, 0);
 packet_ok (buf, );

if rs->buf is reallocated in getpkt, buf points to an out of dated
memory.  This patch removes local 'buf' and uses rs->buf.

gdb:

2014-02-05  Yao Qi  <yao@codesourcery.com>

	* remote.c (remote_pass_signals): Remove local 'buf' and use
	rs->buf.
	(remote_program_signals): Likewise.
Avoid bison-isms when using yacc.

YYPRINT is a bison-ism so c_print_token() ends up being unused when yacc is
used which makes gcc unhappy.  Make sure we only define YYPRINT and
c_print_token() when bison is used to generate the parser.

gdb/ChangeLog:

        * c-exp.y (YYPRINT, c_print_token): Only define if YYBISON is
        defined.