target-mips: Translate breaks and traps into the appropriate signal

GCC and GAS are capable of generating traps or breaks to check for
division by zero.  Additionally, GAS is capable of generating traps
or breaks to check for overflow on certain division and multiplication
operations.  The Linux kernel translates these traps and breaks into
signals.  This patch implements the corresponding feature in QEMU.

Signed-off-by: Meador Inge <meadori@codesourcery.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
