egl: Remove hash table for displays.

The hash table was used to map a display to a handle.  It is simpler to
cast directly.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>

src/egl/main/egldisplay.h

@@ -24,8 +24,10 @@ struct _egl_extensions
 
 struct _egl_display 
 {
+   /* used to link displays */
+   _EGLDisplay *Next;
+
    EGLNativeDisplayType NativeDisplay;
-   EGLDisplay Handle;
 
    const char *DriverName;
    _EGLDriver *Driver;
@@ -58,6 +60,10 @@ struct _egl_display
 };
 
 
+extern void
+_eglFiniDisplay(void);
+
+
 extern _EGLDisplay *
 _eglNewDisplay(NativeDisplayType displayName);