fixed a bug of not checking a function name against named variables

qse/regress/awk/lang-002.awk

@@ -1,6 +1,6 @@
-function f(f)
+function f(x)
 {
-	print f;
+	print x;
 	f("my hello");
 }
 

qse/regress/awk/lang-003.awk

@@ -1,3 +1,3 @@
-# should print 50
-function fn(f) { f = 20; }
-BEGIN { f = 50; fn(100); print f; }
+# should print 50
+function fn(f) { f = 20; }
+BEGIN { f = 50; fn(100); print f; }

qse/regress/awk/lang-004.awk

@@ -1,3 +1,3 @@
 # A function and a named variable cannot have the same name.
-function a () { }
-BEGIN { a = 20; }
+function a () { }
+BEGIN { a = 20; }