make code generation tracing an official debug feature, disable all debug features by default

Cython/Compiler/DebugFlags.py

@@ -2,5 +2,9 @@ debug_disposal_code = 0
 debug_temp_alloc = 0
 debug_coercion = 0
 
-debug_temp_code_comments = 1
+# Write comments into the C code that show where temporary variables
+# are allocated and released
+debug_temp_code_comments = 0
 
+# Write a call trace of the code generation phase into the C code
+debug_trace_code_generation = 0

Cython/Compiler/Nodes.py

@@ -116,8 +116,8 @@ class Node(object):
     #  is_name     boolean              Is a NameNode
     #  is_literal  boolean              Is a ConstNode
 
-    # Uncomment this for debugging.
-    # __metaclass__ = VerboseCodeWriter
+    if DebugFlags.debug_trace_code_generation:
+        __metaclass__ = VerboseCodeWriter
     
     is_name = 0
     is_literal = 0