[flang] Cleanup -- Remove unnecessary inline keyword,

remove unnecessary (void) casts when ignoring
return values, call context_.Say() directly
instead of via messages(), and fix up some
formatting issues using clang-format.

Original-commit: flang-compiler/f18@68e5c02541e1c74abc48327a97291dc2aee530bb
Reviewed-on: https://github.com/flang-compiler/f18/pull/404