fix [2187212] add support for GLESv2 dispatch based on TLS

Instead of using a different function pointer table for ES 1.x and ES 2.x,
we use a single one that is the union (sort|uniq) of both tables. Two
instances of this table are initialized with pointers to GL ES 1.x and GL ES 2.x
entry-points.
When a context is created, we store its version number and when it is bound to a
thread we set the approruiate table based on the stored version.

This introduce no penalty while dispatching gl calls to the right API version.

[Pending Dr No approval for MR1]
diff --git a/opengl/libs/EGL/Loader.h b/opengl/libs/EGL/Loader.h
index 69f6dd5..8659b0b 100644
--- a/opengl/libs/EGL/Loader.h
+++ b/opengl/libs/EGL/Loader.h
@@ -32,7 +32,7 @@
 namespace android {
 // ----------------------------------------------------------------------------
 
-struct gl_hooks_t;
+struct egl_connection_t;
 
 class Loader : public Singleton<Loader>
 {
@@ -69,12 +69,12 @@
 public:
     ~Loader();
     
-    void* open(EGLNativeDisplayType display, int impl, gl_hooks_t* hooks);
+    void* open(EGLNativeDisplayType display, int impl, egl_connection_t* cnx);
     status_t close(void* driver);
     
 private:
     Loader();
-    void *load_driver(const char* driver, gl_hooks_t* hooks, uint32_t mask);
+    void *load_driver(const char* driver, egl_connection_t* cnx, uint32_t mask);
 
     static __attribute__((noinline))
     void init_api(void* dso,