Fix issue with native code optimization of TYA+STA.

This would be changed to STY, but that is invalid if the A value is needed afterward. This could affect the code for certain division operations (after the optimizations in commit 4470626ade).

Here is an example that would be miscompiled:

#pragma optimize -1
#include <stdio.h>
int main(void) {
        unsigned i = 55555;
        unsigned a,b;
        a = b = i / 10000;
        printf("%u %u\n", a,b);
}

Also, remove MVN from the list of "ASafe" instructions since it really isn't, although I don't think this was affecting anything in practice.

Native.pas

@@ -1561,7 +1561,7 @@ var
             [m_bcc,m_bcs,m_beq,m_bmi,m_bne,m_bpl,m_bra,m_brl,m_bvs,m_jml,
              m_jmp_indX,m_jsl,m_lda_abs,m_lda_absx,m_lda_dir,m_lda_dirx,
              m_lda_imm,m_lda_indl,m_lda_indly,m_lda_long,m_lda_longx,m_lda_s,
-             m_mvn,m_pla,m_rtl,m_rts,m_tdc,m_txa,m_tya,m_tsc,d_end,d_bmov,
+             m_pla,m_rtl,m_rts,m_tdc,m_txa,m_tya,m_tsc,d_end,d_bmov,
              d_add,d_pin,d_wrd,d_sym,d_cns] then begin
             ASafe := true;
             goto 1;
@@ -1890,12 +1890,16 @@ var
 
          m_tya:
             if npeep[ns+1].opcode = m_sta_dir then begin
-               npeep[ns+1].opcode := m_sty_dir;
-               Remove(ns);
+               if ASafe(ns+2) then begin
+                  npeep[ns+1].opcode := m_sty_dir;
+                  Remove(ns);
+                  end; {if}
                end {if}
             else if npeep[ns+1].opcode = m_sta_abs then begin
-               npeep[ns+1].opcode := m_sty_abs;
-               Remove(ns);
+               if ASafe(ns+2) then begin
+                  npeep[ns+1].opcode := m_sty_abs;
+                  Remove(ns);
+                  end; {if}
                end; {else if}
 
          m_tyx:

cc.notes

@@ -2051,6 +2051,8 @@ int foo(int[42]);
 
 226. The unary + operator should apply the integer promotions to its operand, e.g. promoting char to int.  This can affect the value of sizeof(+expression).
 
+227. If an unsigned 16-bit value was divided by a constant 1000 or larger, and the result was assigned to two different variables (e.g. a = b = c/1000), incorrect code would be generated when using native code peephole optimization.  (This was a regression introduced in ORCA/C 2.2.0 B6.)
+
 -- Bugs from C 2.1.0 that have been fixed -----------------------------------
 
 1.  In some situations, fread() reread the first 1K or so of the file.