in preparation for releasing distcc version 3.2.

Reviewed by Craig Silverstein.

   -Wwrite-strings when compiling the python extension module,
   due to lack of const correctness in the Python 2.2
   "Python.h" header file.
   This problem was introduced by the fix for distcc issue 26
   <http://code.google.com/p/distcc/issues/detail?id=26>.
   The solution was to explicitly disable these warnings
   with -Wno-write-strings.

2. Centralize the use of gcc-specific compilation options
   in conditional code in configure.ac that is only executed
   if we're using gcc.  Previously include_server/setup.py
   was hard-coding gcc-specific options, regardless of
   whether we're using gcc.

3. Don't use -Wuninitialized if CFLAGS doesn't contain "-O*",
   because -Wuninitialized only works if optimization is enabled.
   This avoids a gcc warning (and hence an error with -Werror)
   about -Wuninitialized not having any effect
   when distcc is configured with "CFLAGS=-g ./configure".

4. Add a new configure option "--disable-Werror".

   For the 3.0 release of distcc, some people porting distcc
   resorted to patching distcc to remove the -Werror option.
   -Werror is useful, so I want to keep it enabled by default,
   but I'd prefer that people are able to port distcc easily,
   hence the configure option.

   This addresses distcc issue 20
   <http://code.google.com/p/distcc/issues/detail?id=20>.

Reviewers: Craig Silverstein

Reviewed by Craig Silverstein.

add a new "--scan-includes" option to distcc which shows
which headers distcc would send to the remote machine in
pump mode, without actually compiling anything.

Reviewed by Craig Silverstein.

Reviewers: Craig Silverstein

Also mention new website, repository and maintainer in NEWS file.