Update comments

Cython/Compiler/ExprNodes.py

@@ -2067,6 +2067,8 @@ class RawCNameExprNode(ExprNode):
 
 class ParallelThreadsAvailableNode(AtomicExprNode):
     """
+    Note: this is disabled and not a valid directive at this moment
+
     Implements cython.parallel.threadsavailable(). If we are called from the
     sequential part of the application, we need to call omp_get_max_threads(),
     and in the parallel part we can just call omp_get_num_threads()

Cython/Compiler/ParseTreeTransforms.py

@@ -959,7 +959,7 @@ class ParallelRangeTransform(CythonTransform, SkipDeclarations):
     module node, set there by InterpretCompilerDirectives.
 
         x = cython.parallel.threadavailable()   -> ParallelThreadAvailableNode
-        with cython.parallel(nogil=True):       -> ParallelWithBlockNode
+        with nogil, cython.parallel.parallel:   -> ParallelWithBlockNode
             print cython.parallel.threadid()    -> ParallelThreadIdNode
             for i in cython.parallel.prange(...):  -> ParallelRangeNode
                 ...