maint: exempt stdio-read.c and stdio-write.c from the cppi check

maint: exempt stdio-read.c and stdio-write.c from the cppi check

* Makefile (sc_cpp_indent_check): Exempt stdio-read.c and stdio-write.c
per Bruno's request, to accommodate this idiom (no space after "#")
even when the function is inside an #if block:
char *
gets (char *s)
#undef gets
{
  ...
}