virglrenderer

Gallium sends the shaders in the order FS-[GS]-[TES]-[TCS]-VS. If an old
shader program is still bound when a new shader is send, then it would use the
old bounds shader of the previous stage to evaluate the shader key and code
creation might create an invalid shader. Hence, if the shader to be translated
is not yet bound ignore the previous stage when evaluating the shader key
(Gurchtan)

Fixes #114

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>