Clean up extra semicolons and braces from loops and conditional statements
and extra braces from function definitions.

This makes the HLSL output considerably easier to read.

TEST=angle_unittests, angle_end2end_tests, dEQP-GLES3.functional.shaders.*,
     WebGL conformance tests
BUG=angleproject:1013

Change-Id: I8180bab7b3d4bda1cdb8e4fb51cf9d8e384dd797
Reviewed-on: https://chromium-review.googlesource.com/273607Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Olli Etuaho <oetuaho@nvidia.com>