[LLVM-C] Finish Up Scope Bindings

Summary: Adds bindings for Module and NameSpace scopes and LLVMDIBuilderCreateForwardDecl, a counterpart to LLVMDIBuilderCreateReplaceableCompositeType.

Reviewers: harlanhaskins, whitequark, deadalnix

Reviewed By: whitequark

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D45934

llvm-svn: 330591