[machdep] use .c for all test files

make_machdep/sizeof_double.c

make_machdep/sizeof_float.c

make_machdep/sizeof_fun.c

make_machdep/sizeof_fun.i

make_machdep/sizeof_int.c

make_machdep/sizeof_long.c

make_machdep/sizeof_longdouble.c

make_machdep/sizeof_longdouble.i

make_machdep/sizeof_longlong.c

make_machdep/sizeof_ptr.c

make_machdep/sizeof_short.c

make_machdep/sizeof_void.c

make_machdep/sizeof_void.i