tcg: initial mips support

Based on a patch from Arnaud Patard (Rtp) <arnaud.patard@rtp-net.org>

A few words about design choices:
* Two registers, at and t0, are reserved for TCG internal use. They are
  useful for bswap and 64-bit ops.
* Most ops supports a constant argument with value 0, which is actually
  mapped to the zero register.
* While the at register is available for constant loading, ops only
  support a limited range of constants. TCG does a better job doing the
  register allocation and constant loading by itself. There are plenty of
  registers available anyway.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

configure

@@ -134,13 +134,15 @@ elif check_define _ARCH_PPC ; then
   else
     cpu="ppc"
   fi
+elif check_define __mips__ ; then
+  cpu="mips"
 else
   cpu=`uname -m`
 fi
 
 target_list=""
 case "$cpu" in
-  alpha|cris|ia64|m68k|microblaze|mips|mips64|ppc|ppc64|sparc64)
+  alpha|cris|ia64|m68k|microblaze|ppc|ppc64|sparc64)
     cpu="$cpu"
   ;;
   i386|i486|i586|i686|i86pc|BePC)
@@ -158,6 +160,9 @@ case "$cpu" in
   parisc|parisc64)
     cpu="hppa"
   ;;
+  mips*)
+    cpu="mips"
+  ;;
   s390*)
     cpu="s390"
   ;;