Remove all RCS @(#) lines and RCS strings

Some folks might think: “you still use RCS”?!?  And we will say,
hey, at least we switched from SCCS to RCS back in … I think it was
around 1994 ... at least we are keeping up! :-) :-) :-)

Logs say that SCCS version 18 became RCS version 19 on 1994 March 18.

RCS served us well.  But now it is time to move on.   And so we are
switching to git.

Calc releases produce a lot of file changes.  In the 125 releases
of calc since 1996, when I started managing calc releases, there
have been 15473 file mods!

help/fopen

@@ -123,10 +123,6 @@ SEE ALSO
 ## received a copy with calc; if not, write to Free Software Foundation, Inc.
 ## 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 ##
-## @(#) $Revision: 30.1 $
-## @(#) $Id: fopen,v 30.1 2007/03/16 11:10:42 chongo Exp $
-## @(#) $Source: /usr/local/src/bin/calc/help/RCS/fopen,v $
-##
 ## Under source code control:	1994/10/27 03:04:17
 ## File existed as early as:	1994
 ##