We only need the typed variable information in our header files.
The entry point and other enum info can be encapsulated better
in the cpp files that call through to the translator. The only
tricky one is the compile options, which we return from our
implementation - put the typedef for these in the ShaderVars
header to fix this.

This should partially work around the problem of shaderlang
for Vulkan and ANGLE's translator (also ShaderLang) using some
identifiers with the same names.

BUG=angleproject:1576

Change-Id: I43c530486498c210796b9e197a6780bf2f7b3afb
Reviewed-on: https://chromium-review.googlesource.com/412423Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>