egl/android: support for EGL_KHR_partial_update

This patch adds support for the EGL_KHR_partial_update extension for
android platform. It passes 36/37 tests in dEQP for EGL_KHR_partial_update.
1 test not supported.

v2: add fallback for eglSetDamageRegionKHR (Tapani)

v3: The native_window_set_surface_damage call is available only from
    Android version 6.0. Reintroduce the ANDROID_VERSION guard and
    advertise extension only if version is >= 6.0. (Emil Velikov)

v4: use newly introduced ANDROID_API_LEVEL guard rather than
    ANDROID_VERSION guard to advertise the extension.The extension
    is advertised only if ANDROID_API_LEVEL >= 23 (Android 6.0 or
    greater). Add fallback function for platforms other than Android.
    Fix possible math overflow. (Emil Velikov)
    Return immediately when n_rects is 0. Place function's entrypoint
    in alphabetical order. (Eric Engestrom)

v5: Replace unnecessary calloc with malloc (Eric)
    Check for BAD_ALLOC error (Emil)
    Check for error in native_window_set_damage_region. (Emil, Tapani,
    Eric).

Signed-off-by: Harish Krupo <harish.krupo.kps@intel.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>

src/egl/main/egldisplay.h

@@ -118,6 +118,7 @@ struct _egl_extensions
    EGLBoolean KHR_image_base;
    EGLBoolean KHR_image_pixmap;
    EGLBoolean KHR_no_config_context;
+   EGLBoolean KHR_partial_update;
    EGLBoolean KHR_reusable_sync;
    EGLBoolean KHR_surfaceless_context;
    EGLBoolean KHR_wait_sync;