Add --debugi-<srcfile> option.

src/V3Unroll.cpp

@@ -59,7 +59,12 @@ private:
     V3Double0		m_statLoops;		// Statistic tracking
     V3Double0		m_statIters;		// Statistic tracking
 
-    //int debug() { return 9; }
+    // METHODS
+    static int debug() {
+	static int level = -1;
+	if (VL_UNLIKELY(level < 0)) level = v3Global.opt.debugSrcLevel(__FILE__);
+	return level;
+    }
 
     // VISITORS
     virtual void visit(AstModule* nodep, AstNUser*) {