Remove support for LLVM runtime multi-threading.

After a number of previous small iterations, the functions
llvm_start_multithreaded() and llvm_stop_multithreaded() have
been reduced essentially to no-ops.  This change removes them
entirely.

Reviewed by: rnk, dblaikie

Differential Revision: http://reviews.llvm.org/D4216

llvm-svn: 211287
diff --git a/llvm/lib/IR/Core.cpp b/llvm/lib/IR/Core.cpp
index 197b6cb..68b9baa 100644
--- a/llvm/lib/IR/Core.cpp
+++ b/llvm/lib/IR/Core.cpp
@@ -2702,11 +2702,10 @@
 /*===-- Threading ------------------------------------------------------===*/
 
 LLVMBool LLVMStartMultithreaded() {
-  return llvm_start_multithreaded();
+  return LLVMIsMultithreaded();
 }
 
 void LLVMStopMultithreaded() {
-  llvm_stop_multithreaded();
 }
 
 LLVMBool LLVMIsMultithreaded() {