libagl: Switch from gralloc to GraphicBufferMapper

Removes all direct references to the gralloc module from libagl and
uses the GraphicBufferMapper class instead when locking and unlocking
buffers.

Also a couple of minor code cleanups to eliminate warnings.

Change-Id: Ie982d375b3152d5f677ab54c2067179b8d34c06d
diff --git a/opengl/libagl/light.cpp b/opengl/libagl/light.cpp
index 479bf7e..e7fe9d7 100644
--- a/opengl/libagl/light.cpp
+++ b/opengl/libagl/light.cpp
@@ -229,7 +229,7 @@
 #endif
         vnorm3(l.normalizedObjPosition.v, l.objPosition.v);
     }
-    const vec4_t eyeViewer = { 0, 0, 0x10000, 0 };
+    const vec4_t eyeViewer = {{{ 0, 0, 0x10000, 0 }}};
 #if OBJECT_SPACE_LIGHTING
     c->transforms.mvui.point3(&c->transforms.mvui,
             &c->lighting.objViewer, &eyeViewer);