Fixed a few compilation warnings.

dlls/x11drv/x11drv_main.c

@@ -281,7 +281,7 @@ BOOL X11DRV_GetScreenSaveActive(void)
 {
     int timeout, temp;
     TSXGetScreenSaver(display, &timeout, &temp, &temp, &temp);
-    return timeout != NULL;
+    return timeout != 0;
 }
 
 /***********************************************************************

graphics/x11drv/bitmap.c

@@ -585,8 +585,8 @@ END:
  */
 Pixmap X11DRV_BITMAP_CreatePixmapFromBitmap( HBITMAP hBmp, HDC hdc )
 {
-    HGLOBAL hPackedDIB = NULL;
-    Pixmap pixmap = NULL;
+    HGLOBAL hPackedDIB = 0;
+    Pixmap pixmap = 0;
 
     /*
      * Create a packed DIB from the bitmap passed to us.

msdos/dosaspi.c

@@ -178,7 +178,7 @@ void ASPI_DOS_HandleInt(CONTEXT86 *context)
 		if( hWNASPI32 == INVALID_HANDLE_VALUE )
 		{
 			TRACE("Loading WNASPI32\n");
-			hWNASPI32 = LoadLibraryExA("WNASPI32", NULL, 0);
+			hWNASPI32 = LoadLibraryExA("WNASPI32", 0, 0);
 		}
 
 		if( hWNASPI32 == INVALID_HANDLE_VALUE )

windows/multimon.c

@@ -29,7 +29,7 @@ HMONITOR WINAPI MonitorFromPoint(POINT ptScreenCoords, DWORD dwFlags)
     {
         return xPRIMARY_MONITOR;
     }
-        return NULL;
+    return (HMONITOR)0;
 }
 
 /***********************************************************************
@@ -45,7 +45,7 @@ HMONITOR WINAPI MonitorFromRect(LPRECT lprcScreenCoords, DWORD dwFlags)
     {
         return xPRIMARY_MONITOR;
     }
-    return NULL;
+    return (HMONITOR)0;
 }
 
 /***********************************************************************
@@ -65,7 +65,7 @@ HMONITOR WINAPI MonitorFromWindow(HWND hWnd, DWORD dwFlags)
         return MonitorFromRect(&wp.rcNormalPosition, dwFlags);
     }
 
-    return NULL;
+    return (HMONITOR)0;
 }
 
 /***********************************************************************