Phase 1 of gcc-in-cxx now complete

I am pleased to report that if you configure gcc with
--enable-build-with-cxx, which causes the core compiler to be built
using a C++ compiler, a bootstrap on x86_64-unknown-linux-gnu now
completes.

I would like to encourage people to try using --enable-build-with-cxx in
other configuration--other bootstraps, cross-compilers--to see how well
it works.  Please let me know if you run into problems that you don't
know how, or don't have time, to fix.

This completes the first phase of the gcc-in-cxx project, which I
started about one year ago at the 2008 GCC Summit.

At this point I personally will probably not work on this project for
some weeks, other than bug fixing.  Further steps on the overall project
of converting gcc to C++ are:

* Write a coding standards document for gcc in C++.

* Convert more code to be compiled as C++ when using
  --enable-build-with-cxx.  Currently the generator programs
  (genattrtab, etc.) and libcpp are still compiled as C.

* Develop some trial patches which require C++, e.g., convert VEC to
  std::vector.

* Test starting the bootstrap with earlier versions of the compiler to
  see which C++ compiler version is required, and document that.

* Petition the steering committee for formal approval to switch to C++.

I do not expect to convert the compiler to require C++ in the 4.5
timeframe.

I encourage anybody who is interested to experiment with these further
steps.

Ian