translator: Fix two bugs that trigger ASSERTs. The first bug was a result of constant-folding a vector swizzle that was out-of-bounds. The second bug was a result of using a semicolon in a preprocessor define. BUG=angleproject:1425 Change-Id: Id6643b1f3e3b13cc021bd721ef2572487fe3c8d3 Reviewed-on: https://chromium-review.googlesource.com/357864 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>