Update required FreeType to 2.8.1

Drop support for FreeType older than 2.8.1. Remove dynamic loading
checks and constant definitions which are now known to exist. Update
includes to no longer require macros. Changes to take advantage of
thread safety will be done later.

Change-Id: Idf82147cad0df8315c6737e878ec6750537c7b28
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/429898
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
1 file changed