locking: teach Clang's -Wthread-safety to cope with our scoped lock macros

This allows us to use function/variable/class attributes to specify locking
requisites, allowing problems to be detected during static analysis.

This works perfectly with newer Clang versions (tested with 3.3-3.7). For older
versions (tested 3.2), it compiles fine but spews lots of false-positives.

src/sync.h

@@ -101,7 +101,7 @@ void PrintLockContention(const char* pszName, const char* pszFile, int nLine);
 
 /** Wrapper around boost::unique_lock<Mutex> */
 template <typename Mutex>
-class CMutexLock
+class SCOPED_LOCKABLE CMutexLock
 {
 private:
     boost::unique_lock<Mutex> lock;
@@ -129,7 +129,7 @@ private:
     }
 
 public:
-    CMutexLock(Mutex& mutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false) : lock(mutexIn, boost::defer_lock)
+    CMutexLock(Mutex& mutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(mutexIn) : lock(mutexIn, boost::defer_lock)
     {
         if (fTry)
             TryEnter(pszName, pszFile, nLine);
@@ -137,7 +137,7 @@ public:
             Enter(pszName, pszFile, nLine);
     }
 
-    CMutexLock(Mutex* pmutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false)
+    CMutexLock(Mutex* pmutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(pmutexIn)
     {
         if (!pmutexIn) return;
 
@@ -148,7 +148,7 @@ public:
             Enter(pszName, pszFile, nLine);
     }
 
-    ~CMutexLock()
+    ~CMutexLock() UNLOCK_FUNCTION()
     {
         if (lock.owns_lock())
             LeaveCritical();