Prevent structs/interface-blocks from claiming builtin types.

Structs and interface blocks allow a trailing identifier which is added
to the symbol table. This identifier is now prohibited from
overlapping built-in types.

Change-Id: I33b9d6156a27ce017e6744a05979748c04a04767
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/489516
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
4 files changed