Implement generic mad_sat

v2: Fix trailing whitespace
    Fix signed long overflow
    improve comment

Signed-off-by: Jan Vesely <jan.vesely at rutgers.edu>
Add int3/uint3 to integer-gentype.inc

These were missing and caused mad24/mul24 with int3/uint3 arg type to fail

Signed-off-by: Aaron Watry <awatry@gmail.com>
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>