add note on maintainance status

[core] Add builders for exception handlign stuff

[core] Add support for LLVM operand bundle

[core] Add unreachable and resume builders

[core] Re-enable doc tests

[core] Fix issue with RustDoc lists being interpreted as doctests

[core] Fix issues with values in scoped unsafe blocks

[core] Fix incorrect arg name issue in Builder.build_ret()

[core] Start on builder.build_invoke() fn

[core] Add documentation in llvm::Builder

[core] Start on build...() methods for LLVM builder

[core] Fix some issues in new LLVM bindings

[core] LLVM refs get Drop impls for free too

[core] Begin on better safe LLVM wrapper

Fix new llvm_version() function