[RFA] Add support for --without-zlib (take 2)

[Joel Brobecker]

> As long as it is not used by GCC configury, I don't think people mind  
> here.  The only suggestion I have is to have [default=auto] somewhere in  
> the help string.

OK - I will add it.

> BTW, zlib is always distributed with GCC so we always include zlib  
> support (and instead of --with-zlib, there is a --with-system-zlib flag  
> that does what you expect).  Maybe you could do the same for binutils  
> and gdb?  In that case, centralizing the test in AM_ZLIB is certainly  
> desirable, and gcc may pick up the macro later or parts of it.

Yes, Tom Tromey also mentioned that. Right now, I am more interested
in being able to build without zlib (we find its usefulness in GDB to be
marginal for us), but maybe the day will come when GDB/binutils must be
built with zlib, in which case I'll adjust zlib.m4 accordingly.

Thank you!
-- 
Joel