Add more detailed symbol type categorization, based on a swift patch by

Greg Clayton a few years ago.

My patch to augment the symbol table in Mach-O files with the
dyld trie exports data structure only categorized symbols as code
or data, but Greg Clayton had a patch to do something similar to
swift a few years ago that had a more extensive categorization of
symbols, as well as extracting some objc class/ivar names from the
entries. This patch is basically just Greg's, updated a bit and
with a test case added to it.

<rdar://problem/50791451>

Differential Revision: https://reviews.llvm.org/D77369