Fix codegen bug with pc_bno in some cases with a 64-bit right operand.

The desired location for the quad result was not saved, so it could be overwritten when generating code for the left operand. This could result in incorrect code that might trash the stack.

Here is an example affected by this:

#pragma optimize 1
int main(void) {
        long long a, b=2;
        char c = (a=1,b);
}

Gen.pas

@@ -5444,11 +5444,14 @@ procedure GenTree {op: icptr};
 
    var
       lLong: longType;			{requested address type}
+      lQuad: quadType;
 
    begin {GenBno}
    lLong := gLong;
+   lQuad := gQuad;
    GenTree(op^.left);
    gLong := lLong;
+   gQuad := lQuad;
    GenTree(op^.right);
    end; {GenBno}