optimise away unneeded flag sets

- especially useful for thumb code and larger max block sizes
- can still be improved upon

src/ARM_InstrInfo.h

@@ -215,11 +215,24 @@ enum
     tk_Count
 };
 
+enum
+{
+    flag_N = 1 << 3,
+    flag_Z = 1 << 2,
+    flag_C = 1 << 1,
+    flag_V = 1 << 0,
+};
+
 struct Info
 {
     u16 DstRegs, SrcRegs;
     u16 Kind;
 
+    u8 ReadFlags;
+    // lower 4 bits - set always
+    // upper 4 bits - might set flag
+    u8 WriteFlags;
+
     bool EndBlock;
     bool Branches()
     {