[LLVM-C] Add DIBuilder Bindings For ObjC Classes

Summary: Add LLVMDIBuilderCreateObjCIVar, LLVMDIBuilderCreateObjCProperty, and LLVMDIBuilderCreateInheritance to allow declaring metadata for Objective-C class hierarchies and their associated properties and instance variables.

Reviewers: whitequark, deadalnix

Reviewed By: whitequark

Subscribers: harlanhaskins, llvm-commits

Differential Revision: https://reviews.llvm.org/D47123

llvm-svn: 332850