* gcc.dg/tree-ssa/pr21090.c: Do folding scan check only for
        target { keeps_null_pointer_checks }.
        * c-c++-common/simulate-thread/bitfields-2.c: Run test only for
        target { ! int16 }.
        * gcc.dg/tree-ssa/pr54245.c: Do slsr scan only for target { ! int16 }.
        * gcc.dg/tree-ssa/slsr-1.c: Adjust multiplicators to scan for for
        target { int16 }.
        * gcc.dg/tree-ssa/slsr-2.c, gcc.dg/tree-ssa/slsr-27.c: Likewise.
        * gcc.dg/tree-ssa/slsr-28.c, gcc.dg/tree-ssa/slsr-29.c: Likewise.
        * gcc.dg/tree-ssa/slsr-3.c, gcc.dg/tree-ssa/ssa-ccp-23.c: Likewise.
        * lib/target-supports.exp (check_effective_target_int32): New proc.
        * gcc.dg/torture/pr53366-1.c: Only run for target { size32plus }.
        * gcc.dg/tree-ssa/pr42585.c: Add avr*-*-* to list of targets to
        exclude from scan test.
        * gcc.dg/torture/pr56488.c: Only run for target { size32plus }.
        * c-common.c (same_scalar_type_ignoring_signedness): Also
        accept short/int as equivalent if they have the same type.