restructure: move el compiler content into lang/

lang/tests/text/examples/split-lines.el

@@ -0,0 +1,10 @@
+// split-lines.el — \n-delimited split, \r\n folded, trailing empty dropped.
+// "alpha\nbeta\r\ngamma\n" -> ["alpha", "beta", "gamma"], len = 3.
+fn run_test() -> Int {
+    let lines: [String] = str_split_lines("alpha\nbeta\r\ngamma\n")
+    return native_list_len(lines)
+}
+
+fn main() -> Void {
+    println(int_to_str(run_test()))
+}