Disable a native-code optimization that was generating bad code for %.

Specifically, it converted PLX followed by PHA to STA 1,S. This is invalid if the x value is actually used, which is a case that can come up in the code now generated for the % operator.

It might be possible to re-enable this optimization with tighter checks about where it's applied, but I don't think it's terribly important.

The below program demonstrates an example that was being miscompiled:

#pragma optimize -1
#include <stdio.h>
int main(void) {
        int a = 100, b = 200, c = 3, d = 4;
        printf("%i\n", (a+b) % (c+d)); /* should be 6 */
}

Native.pas

@@ -1666,7 +1666,8 @@ var
                Remove(ns);
                end; {if}
 
-         m_plx:
+         {disabled - can generate bad code if the x value is used}
+         {m_plx:
             if npeep[ns+1].opcode = m_pha then begin
                opcode := m_sta_s;
                mode := direct;