Remove lib-src/fakemail.c.

Remove lib-src/fakemail.c.

* lib-src/fakemail.c: Remove file.

* lib-src/Makefile.in (UTILITIES): Remove fakemail${EXEEXT}.
(fakemail${EXEEXT}): Remove rule.

* lib-src/makefile.w32-in ($(BLD)/fakemail.exe, fakemail)
($(BLD)/fakemail.$(O)): Remove.

* lisp/mail/sendmail.el (sendmail-program): Fall back to just "sendmail".

* lisp/mail/feedmail.el: Update commentary.

* doc/emacs/ack.texi (Acknowledgments): Remove fakemail.c.

* etc/NEWS: Mention this.

* INSTALL: Remove fakemail.