The instruction following STI is always executed, even if an interrupt

is pending. Fixes Windows 9x boot broken by SYSENTER commit.

src/x86_ops_flag.h

@@ -85,12 +85,13 @@ static int opSTI(uint32_t fetchdat)
         else
                 cpu_state.flags |= I_FLAG;
 
-/*TODO - should end block after 1 further instruction*/
-//        CPU_BLOCK_END();
-                                
+        /*First instruction after STI will always execute, regardless of whether
+          there is a pending interrupt*/
+        cpu_end_block_after_ins = 2;
+
         CLOCK_CYCLES(2);
         PREFETCH_RUN(2, 1, -1, 0,0,0,0, 0);
-        return 1;
+        return 0;
 }
 
 static int opSAHF(uint32_t fetchdat)