Internals: Standardize debug() function generation. No functional change intended.

src/V3Descope.cpp

@@ -58,11 +58,7 @@ private:
     FuncMmap		m_modFuncs;	// Name of public functions added
 
     // METHODS
-    static int debug() {
-	static int level = -1;
-	if (VL_UNLIKELY(level < 0)) level = v3Global.opt.debugSrcLevel(__FILE__);
-	return level;
-    }
+    VL_DEBUG_FUNC;  // Declare debug()
 
     static bool modIsSingleton(AstNodeModule* modp) {
         // True iff there's exactly one instance of this module in the design.