Make ScreenRes a normal function instead of quirk "sub" - so it can be called as a function with a return value, or so the arg list can be wrapped in parentheses
Some internal cleanup, where allowances are no longer needed for a quirk ScreenRes
tests: Fix faulty Byref result test cases

1. function declared with INTEGER PTR result when it should have been
   INTEGER

2. EXTERN "C++" causing function pointers inside of it to use CDECL
   implicitly, while other function pointers outside the EXTERN used the
   default calling convention, causing mismatches due to STDCALL on Win32
Fix error recovery if calls to BYREF result function fail

cProcArgList() can return a CONST for error recovery, in which case the
assert( astIsCALL() ) in astBuildByrefResultDeref() complained.
Now astBuildByrefResultDeref() takes care of all the checks itself.