Store the commit date in version.h, and in the DLL properties.
This will allow Chrome, or other apps who reference ANGLE internally,
to pull chronological version information about ANGLE.

BUG=angle:529
Change-Id: I307bf44103913aaaeb875a2e3ade1fab77838c48
Reviewed-on: https://chromium-review.googlesource.com/182142Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>