Corrects interaction of BITMAPBIT with buffered display bitmap

Two problems fixed:
  * only in the case of a software cursor is it necessary to check if
  the bit being altered is within the region of the display covered by
  the cursor, and if it is, the cursor must be hidden before operating
  on the screen bitmap
  * SDL as well as X requires modifications to the screen bitmap be
  flushed to the actual display.

src/misc7.c

@@ -43,7 +43,9 @@ LispPTR N_OP_misc7(LispPTR arg1, LispPTR arg2, LispPTR arg3, LispPTR arg4, LispP
   int offset;
   DLword bmdata;
   DLword bmmask;
+#ifdef REALCURSOR
   int displayflg;
+#endif
 
   DBPRINT(("MISC7 op with alpha byte %d.\n", alpha));
 
@@ -58,7 +60,11 @@ LispPTR N_OP_misc7(LispPTR arg1, LispPTR arg2, LispPTR arg3, LispPTR arg4, LispP
 
   DBPRINT(("MISC7 args OK.\n"));
 
+#ifdef REALCURSOR
   displayflg = n_new_cursorin(base, x, (heightminus1 - y), 1, 1);
+  if (displayflg)
+    HideCursor();
+#endif
 
 /* Bitmaps use a positive integer coordinate system with the lower left
    corner pixel at coordinate (0, 0). Storage is allocated in 16-bit words
@@ -79,12 +85,12 @@ LispPTR N_OP_misc7(LispPTR arg1, LispPTR arg2, LispPTR arg3, LispPTR arg4, LispP
   }
 
 
-#ifdef XWINDOW
+#if defined(XWINDOW) || defined(SDL)
   if (in_display_segment(base)) {
     /* NB: base + offset doesn't need WORDPTR() wrapper */
     flush_display_ptrregion(base + offset, 0, 16, 1);
   }
-#endif /* XWINDOW */
+#endif /* XWINDOW || SDL */
 
   ScreenLocked = NIL;
   DBPRINT(("FBITMAPBIT old bit = 0x%x.\n", oldbit));