Removed main.h dependency from rpcserver.cpp

Rebased by @laanwj:

- update for RPC methods added since 84d13ee: setmocktime,
  invalidateblock, reconsiderblock. Only the first, setmocktime, required a change,
  the other two are thread safe.

src/sync.h

@@ -142,6 +142,17 @@ public:
             Enter(pszName, pszFile, nLine);
     }
 
+    CMutexLock(Mutex* pmutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false)
+    {
+        if (!pmutexIn) return;
+
+        lock = boost::unique_lock<Mutex>(*pmutexIn, boost::defer_lock);
+        if (fTry)
+            TryEnter(pszName, pszFile, nLine);
+        else
+            Enter(pszName, pszFile, nLine);
+    }
+
     ~CMutexLock()
     {
         if (lock.owns_lock())