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

src/V3Branch.cpp

@@ -57,11 +57,7 @@ private:
     CFuncVec	m_cfuncsp;	// List of all tasks
 
     // 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()
 
     void reset() {
 	m_likely = false;