Make cobol.cbl a well-formed COBOL program.

- Start statements after seven columns.
- Use lowercase, as it is less hideous.
- Terminate `display` properly with `end-display`.
- Make the `program-id` field match the file name.

c/cobol.cbl

@@ -1,6 +1,6 @@
-IDENTIFICATION DIVISION.
+       identification division.
-PROGRAM-ID. HELLOWORLD.
+       program-id. cobol.
-PROCEDURE DIVISION.
+       procedure division.
-MAIN.
+       main.
-  DISPLAY 'Hello, world.'.
+           display 'Hello, world.' end-display.
-  STOP RUN.
+           stop run.