Fix code generation for qualified struct or union function parameters.

They were not being properly recognized as structs/unions, so they were being passed by address rather than by value as they should be.

Here is an example affected by this:

struct S {int a,b,c,d;};

int f(struct S s) {
    return s.a + s.b + s.c + s.d;
}

int main(void) {
    const struct S s = {1,2,3,4};
    return f(s);
}

Expression.pas

@@ -3453,11 +3453,17 @@ var
       while tp <> nil do begin
          if tp^.middle <> nil then begin
             GenerateCode(tp^.middle);
-            if expressionType^.kind in [structType,unionType] then begin
-               if expressionType^.size & $FFFF8000 <> 0 then
-                  Error(61);
-               Gen1t(pc_ldc, long(expressionType^.size).lsw, cgWord);
-               Gen0(pc_psh);
+            if expressionType^.kind in [structType,unionType,definedType]
+               then begin
+               tType := expressionType;
+               while tType^.kind = definedType do
+                  tType := tType^.dType;
+               if tType^.kind in [structType,unionType] then begin
+                  if tType^.size & $FFFF8000 <> 0 then
+                     Error(61);
+                  Gen1t(pc_ldc, long(tType^.size).lsw, cgWord);
+                  Gen0(pc_psh);
+                  end; {if}
                end; {if}
             if fmt <> fmt_none then begin
                new(tfp);

cc.notes

@@ -1620,6 +1620,8 @@ If you use #pragma debug 0x0010 to enable stack check debug code, the compiler w
 
 15. Native code peephole optimization might produce invalid code in some obscure circumstances where one element of a global or static array was decremented and then another element of the same array was accessed immediately thereafter.
 
+16. When an expression of const- or volatile-qualified struct or union type was passed as a function parameter, incorrect code would be generated.  This could lead to incorrect program behavior or crashes.
+
 -- Bugs from C 2.1.1 B3 that have been fixed in C 2.2.0 ---------------------
 
 1.  There were various bugs that could cause incorrect code to be generated in certain cases.  Some of these were specific to certain optimization passes, alone or in combination.