[Orc][RPC] Add a class-method version of addHandler to MultiThreadedRPCEndpoint.
[Orc][RPC] Add a class-method version of addHandler to MultiThreadedRPCEndpoint.

This brings MultiThreadedRPCEndpoint's addHandler API in-line with
SingleThreadedRPCEndpoint's.

This will be tested in an up-coming unit-test for MultiThreadedRPCEndpoint.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@291376 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm