Remove extern errno declarations.

Remove extern errno declarations.
* xterm.c:
* xrdb.c:
* w32term.c:
* unexec.c:
* unexaix.c:
* sysdep.c:
* process.c:
* lread.c:
* keyboard.c:
* floatfns.c:
* filelock.c:
* fileio.c:
* emacs.c (main):
* ecrt0.c:
* dispnew.c:
* callproc.c:
* buffer.c: Remove errno extern declarations.
* s/netbsd.h (NEED_ERRNO): Remove.

* movemail.c:
* etags.c:
* emacsclient.c: Remove extern errno declarations.