Don't use Interlocked.Increment/Decrement when we have the lock

It makes it hard to figure out what needs to be accessed atomically and what
doesn't. Since we have the _reentrances lock for both the increment and the
decrement, there is no need for the explicit Interlocked call here.

Author: mqudsi

AsyncLock/AsyncLock.cs

@@ -273,7 +273,7 @@ private bool InnerTryEnter(bool synchronous = false)
                     }
 
                     // We can go in
-                    Interlocked.Increment(ref _parent._reentrances);
+                    _parent._reentrances += 1;
                     result = true;
                     return result;
                 }
@@ -302,7 +302,7 @@ public void Dispose()
                 @this._parent._reentrancy.Wait();
                 try
                 {
-                    Interlocked.Decrement(ref @this._parent._reentrances);
+                    @this._parent._reentrances -= 1;
                     @this._parent._owningId = oldId;
                     @this._parent._owningThreadId = oldThreadId;
                     if (@this._parent._reentrances == 0)