Backported the codegen_accumulate functionality to the old recompiler, so Windows 98 first edition on i686 CPU's can stay fixed without i686 timings getting messed up.

src/cpu/codegen_accumulate.h

@@ -0,0 +1,13 @@
+enum
+{
+        ACCREG_ins    = 0,
+        ACCREG_cycles = 1,
+        
+        ACCREG_COUNT
+};
+
+struct ir_data_t;
+
+void codegen_accumulate(int acc_reg, int delta);
+void codegen_accumulate_flush(void);
+void codegen_accumulate_reset();