Fix _RGB32() optional arguments

The new optional arguments for functions broke _RGB32() because it uses
some custom flags ('overloaded' and 'minargs' on the id Type) to control
its parameter passing. You are allowed passing any number from 1 to 4 args
to `func__rgb32` and there are 4 overloaded C++ functions that will get
picked from. This is different from how this typically would work, with
all 4 parameters always passed and an extra argument to specify the
parameters that were passed.

Rather than change `func__rgb32` I simply adjusted the optional argument
logic to account for the flags used by `_RGB32()` - if the `overloaded`
flag is set, then we don't need to add extra `NULL` parameters for any
parameter that wasn't specified in the argument list. Instead we simply
don't emit anything for those.

source/qb64pe.bas

@@ -17783,7 +17783,9 @@ FUNCTION evaluatefunc$ (a2$, args AS LONG, typ AS LONG)
         NEXT
 
         ' Add on any extra optional arguments that were not provided
-        IF curarg <= id2.args THEN
+        '
+        ' Overloaded functions do not require the omited arguments to be provided
+        IF curarg <= id2.args AND NOT id2.overloaded THEN
             FOR i = curarg TO id2.args
                 IF i = 1 THEN r$ = r$ + "NULL" ELSE r$ = r$ + ",NULL"
             NEXT

tests/compile_tests/colors/test.bas

@@ -0,0 +1,8 @@
+$Console:Only
+
+Print "Grey, max alpha: "; Hex$(_RGB32(&H7F))
+Print "Grey, half alpha: "; Hex$(_RGB32(&H7F, &H7F))
+Print "Grey, max alpha: "; Hex$(_RGB32(&H7F, &H7F, &H7F))
+Print "Grey, half alpha: "; Hex$(_RGB32(&H7F, &H7F, &H7F, &H7F))
+
+System

tests/compile_tests/colors/test.output

@@ -0,0 +1,4 @@
+Grey, max alpha: FF7F7F7F
+Grey, half alpha: 7F7F7F7F
+Grey, max alpha: FF7F7F7F
+Grey, half alpha: 7F7F7F7F