don't use compile-time configuration of libgui as much as possible

We now detect at runtime which sync features to use, which
allows us to remove a lot of the compile-time configuration
options. There  is still one option though, to disable
KHR_fence_sync on some devices (which are more efficient
without it).

- added a backdoor to get the vendor's EGL strings

the new logic is:
- use always ANDROID_native_fence_sync if available
- fallback to KHR_fence_sync if available and not disabled
  by the compile-time option
- use KHR_wait_sync if available and either of the above is
  enabled

Change-Id: I9c4b49d9ff1151faf902cc93bd53ea5f205aaabf
diff --git a/services/surfaceflinger/GLExtensions.cpp b/services/surfaceflinger/GLExtensions.cpp
index 0cbf4b1..e5fb083 100644
--- a/services/surfaceflinger/GLExtensions.cpp
+++ b/services/surfaceflinger/GLExtensions.cpp
@@ -80,7 +80,7 @@
         mHaveDirectTexture = true;
     }
 #else
-#warning "EGL_ANDROID_image_native_buffer not supported"
+#error "EGL_ANDROID_image_native_buffer not supported"
 #endif
 
     if (hasExtension("GL_ARB_texture_non_power_of_two")) {