renumbers error testers basing on 5000.

fixed a compiler bug not checking the lower bound of block depth in find_variable_backward_with_word()

t/var-5001.err

@@ -0,0 +1,25 @@
+defclass A | a | {
+	defun ::* init1() {
+		| b |
+		set b (+ 1 2);
+		set a b;
+		printf "init to %d\n" a;
+		return self;
+	};
+
+	{
+		## this must not be allowed at this level. if it's allowed,
+		## it should be at the top-level which is above the class level. this is confusing.
+		| j | ##ERROR: syntax error - variable declaration disallowed in class init scope
+		set j 20;
+		printf ">>> %d\n" j;
+	}
+
+	defun ::* init2() {
+		| b |
+		set b (+ 10 20);
+		set a b;
+		printf "init to %d\n" a;
+		return self;
+	};
+};