Remove PackedVersion from MachOLinkingContext and replace with uint32_t
and a parsePackedVersion() utility.

Patch by Joe Ranieri



git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@190451 91177308-0d34-0410-b5e6-96231b3b80d8
Support darwin linker options: 
-current_version, -compatibility_version, and -install_name.

Patch by Joe Ranieri



git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@190452 91177308-0d34-0410-b5e6-96231b3b80d8