Add 'ENUM_...._SETTINGS' flag and make use of it in the X11DRV code.

dlls/x11drv/settings.c

@@ -170,12 +170,12 @@ BOOL X11DRV_EnumDisplaySettingsEx( LPCWSTR name, DWORD n, LPDEVMODEW devmode, DW
     devmode->dmDisplayFlags = 0;
     devmode->dmDisplayFrequency = 0;
     devmode->dmSize = sizeof(DEVMODEW);
-    if (n == (DWORD)-1)
+    if (n == ENUM_CURRENT_SETTINGS)
     {
         TRACE("mode %ld (current) -- getting current mode (%s)\n", n, handler_name);
         n = pGetCurrentMode();
     }
-    if (n == (DWORD)-2)
+    if (n == ENUM_REGISTRY_SETTINGS)
     {
         TRACE("mode %ld (registry) -- getting default mode (%s)\n", n, handler_name);
         n = dd_mode_default;

include/winuser.h

@@ -1304,6 +1304,10 @@ BOOL        WINAPI SetSysColors(INT,const INT*,const COLORREF*);
 #define IDTRYAGAIN         10
 #define IDCONTINUE         11
 
+/* Used for EnumDisplaySettingsEx */
+#define ENUM_CURRENT_SETTINGS  ((DWORD) -1)
+#define ENUM_REGISTRY_SETTINGS ((DWORD) -2)
+
 /****** Window classes ******/
 
 typedef struct tagCREATESTRUCTA