mtcp_restart exits if no match, MTCP_SIGNATURE

* It used to verbosely make 20 tries at end of file, and then abort.
  Now, it prints a simple error statement, and exits with 'return 1'.

Added NEWS for 2.4.0 release

Tagging 2.3.1

Tagging 2.3.

Tagging 2.2.2.

Tagging 2.2.1.

Tagging 2.2.

Tagging 2.1.1.

Revert 2633 (accidental tagging to the wrong dir).

Tagging 2.0.3.