Move inline functions with static-locals to implementation files

Summary:
This refactors inline functions defined in headers which had static locals
so that their definition is moved to the corresponding implementation file.

Reviewed By: yfeldblum

Differential Revision: D4049175

fbshipit-source-id: 56eeb82eb23b04c3b9940d803d05050949aa5ef9

folly/experimental/RCUUtils.cpp

@@ -49,4 +49,10 @@ bool RCURegisterThread() {
   return ret;
 }
 
+RCUReadLock& RCUReadLock::instance() {
+  // Both lock and unlock are static, so no need to worry about destruction
+  // order
+  static RCUReadLock instance;
+  return instance;
+}
 }

folly/experimental/RCUUtils.h

@@ -30,12 +30,7 @@ bool RCURegisterThread();
 
 class RCUReadLock {
  public:
-  static RCUReadLock& instance() {
-    // Both lock and unlock are static, so no need to worry about destruction
-    // order
-    static RCUReadLock instance;
-    return instance;
-  }
+  static RCUReadLock& instance();
 
   static void lock() {
     assert(RCURegisterThread() == false);