gdb: fix debugging of MIPS(el) applications

GDB previously failed with the following:

root@OpenWrt:/# gdb busybox
[snip]
(gdb) r
Starting program: /bin/busybox
GDB bug: target.c (gdb_signal_from_host): unrecognized real-time signal

Signed-off-by: Florian Fainelli <florian@openwrt.org>

SVN-Revision: 34258

package/devel/gdb/patches/001-gdb-pr14523-mips-signal-number.patch

+See http://sourceware.org/bugzilla/show_bug.cgi?id=14523
+---
+--- gdb-7.5.org/gdb/common/signals.c	2012-05-24 18:51:37.000000000 +0200
++++ gdb-7.5.org/gdb/common/signals.c	2012-08-29 22:32:07.000000000 +0200
+@@ -346,6 +346,11 @@ 
+       else if (64 <= hostsig && hostsig <= 127)
+ 	return (enum gdb_signal)
+ 	  (hostsig - 64 + (int) GDB_SIGNAL_REALTIME_64);
++      else if (hostsig == 128)
++	/* Some platforms, such as Linux MIPS, have NSIG == 128, in which case
++	   signal 128 is the highest realtime signal. There is no constant for
++	   that though. */
++	return GDB_SIGNAL_UNKNOWN;
+       else
+ 	error (_("GDB bug: target.c (gdb_signal_from_host): "
+ 	       "unrecognized real-time signal"));