[mach-o] Add support for parsing __eh_frame section. Generalize support for whether symbols in a section are ignored or illegal

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@209858 91177308-0d34-0410-b5e6-96231b3b80d8
[mach-0] Add support for parsing compact unwind info section

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@209865 91177308-0d34-0410-b5e6-96231b3b80d8