simple WebP viewer, based on OpenGL

Quite handy and simple (for now).
It's not yet incorporated within the build system (autotools or
makefile.unix), because it gets complicated with OpenGL. TODO(later).

For now, there's some ready-to-use command line for compiling on Linux
or Mac in the header of vwebp.c

Later, this tool will be supplemented with support for animation,
tiling, zooming, etc.

Change-Id: I292972cea4862536afbe8c9ec444c590d152f086

README

@@ -228,6 +228,18 @@ Use following options to convert into alternate image formats:
   -v     ....... verbose (e.g. print encoding/decoding times)
   -noasm ....... disable all assembly optimizations.
 
+Visualization tool:
+===================
+
+There's a little self-serve visualization tool called 'vwebp' under the
+examples/ directory. It uses OpenGL to open a simple drawing window and show
+a decoded WebP file. It's not yet integrated in the automake or makefile.unix
+build system, but you can try to manually compile it using the recommendations
+at the top of the source file.
+
+Usage: 'vwebp my_picture.webp'
+
+
 Encoding API:
 =============