There are many types of statements after which a semicolon is not
needed. Skip writing the semicolon in HLSL output in these cases to
make the output code more readable.

BUG=angleproject:1013
TEST=angle_end2end_tests

Change-Id: I8f6a5e4ecfe5def456fdf19cca5ca451c13d7f35
Reviewed-on: https://chromium-review.googlesource.com/718420
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>