Rename LLVM_MULTITHREADED define and fix build without threads.

Patch by Arrowdodger.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140064 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/configure b/configure
index 920040c..8c59539 100755
--- a/configure
+++ b/configure
@@ -21027,7 +21027,7 @@
 echo "${ECHO_T}yes" >&6; }
 
 cat >>confdefs.h <<\_ACEOF
-#define LLVM_MULTITHREADED 1
+#define LLVM_HAS_ATOMICS 1
 _ACEOF
 
 else
@@ -21038,7 +21038,7 @@
 echo "${ECHO_T}no" >&6; }
 
 cat >>confdefs.h <<\_ACEOF
-#define LLVM_MULTITHREADED 0
+#define LLVM_HAS_ATOMICS 0
 _ACEOF
 
   { echo "$as_me:$LINENO: WARNING: LLVM will be built thread-unsafe because atomic builtins are missing" >&5