Misc_Helpers: f_str_split(): Fix parse with len(delimiter) > 1

Change-Id: I1ac53635deea82a501f2a8c7a94faf501ddf7afd

library/Misc_Helpers.ttcn

@@ -94,7 +94,7 @@ function f_str_split(charstring str, charstring delim := "\n") return ro_charstr
 		if (delim_pos > pos) {
 			parts := parts & { substr(str, pos, delim_pos - pos) };
 		}
-		pos := delim_pos + 1;
+		pos := delim_pos + lengthof(delim);
 	}
 	return parts;
 }