egl: definitions for EXT_image_dma_buf_import

egl: definitions for EXT_image_dma_buf_import

As specified in:

http://www.khronos.org/registry/egl/extensions/EXT/EGL_EXT_image_dma_buf_import.txt

Checking for the valid fourcc values is left for drivers avoiding
dependency to drm header files here.

v2: enforce EGL_NO_CONTEXT

v3: declare the extension as EGL (not GLES)

v4: do not update eglext.h manually but rely on update from
    Khronos instead

v5: (Eric) report invalid context as EGL_BAD_PARAMETER instead of as
    EGL_BAD_CONTEXT

v6: (Chad) fix the checking for valid hints. Before all values were
    rejected.

v7: (Chad) comment style change from

    /**
     * Multi-
     * line

    into

    /* Multi-
     * line

Signed-off-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>