Replace gen_arith2 generic macro and dyngon ops by instruction specific
optimized TCG code.
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5235 c046a42c-6fe2-441c-8c8c-71466251a162