[AC21.5R21.4] etags and implicit tags

[Stephen J. Turnbull]

Vin, if you're thinking about releasing soon, let me know.  I'd like
to conform to Francesco's suggestion for the next releases of 21.4 and
21.5, and don't think it will be too hard.

Francesco Potorti` writes:

 > I would prefer avoiding this, if possible, by defining VERSION in the
 > Makefile as appropriate.

That makes sense.  This is not entirely trivial, as VERSION is
computed in our Makefile as

version=@version@

and that of course is done by configure.  But it shouldn't be too hard.

 > >-# if PRINT_UNDOCUMENTED_OPTIONS_HELP
 > >+# ifdef PRINT_UNDOCUMENTED_OPTIONS_HELP
 > 
 > You changed this to quench a warning, as I understand.  However, I do
 > not get any, using gcc 4.1.2 with -pedantic and -Wall.  What compiler do
 > you use?

Compiler is:
powerpc-apple-darwin8-gcc-4.0.1 (GCC) 4.0.1 (Apple Computer, Inc. build 5247)

Compile command is:
gcc   -Wall -Wno-switch -Wundef -Wsign-compare -Wno-char-subscripts -Wpacked -Wpointer-arith -Wunused-parameter -g  

I suppose it's the -Wundef.  I'm not sure why that was added, and
would rather not remove it for that reason.  I'm not sure that we're
100% clean at this instant, but not too long ago XEmacs had exactly
one compile warning, caused by the getopt stuff in etags.  This is not
a particularly burdensome discipline.