VS2017 took issue with treating size_t and uint32_t the same. It also
couldn't find various alphanumeric is* functions without the <cctype>
header. Gcc complainted about a variable potentially used uninitialized.
Change-Id: I452b68c6597bae254f32e5a350656e65c8934b6e
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/18901
Reviewed-by: dan sinclair <dsinclair@google.com>