Also move the block layout encoding utilities to the common folder.
The combined changes allow us to include the shader and block code
into both libGLESv2 and the translator separately. This in turn
fixes the Chromium component build, where we were calling internal
translator functions directly from libGLESv2.

BUG=angle:568

Change-Id: Ibcfa2c936a7c737ad515c10bd24061ff39ee5747
Reviewed-on: https://chromium-review.googlesource.com/192891Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>