[PATCH] header search

Find attached patch which fixes <cstddef> issue on some linux distros and adds
yet more C++ search dirs for various linux distros. Details follow.

  Updated C++ include header search paths for various Debian/Ubuntu and Fedora
  linux distros. The main changes are static ordering of directories to check
  for GNU c++ includes:

        - newer versions of libstdc++ are checked for first
        - distros listing is reverse chronological order
        - more clear that N-distros need the same dir check

  Tracking for the following new distros has been added; unless otherwise noted,
  all adds have been validated to not break things by building clang selfhost:

        - Ubuntu 10.04 LTS 64-bit, 32-bit
        - Ubuntu 9.10 32-bit
        - Ubuntu 9.04 64-bit
        - Ubuntu 8.10 64-bit
        - Ubuntu 8.04 LTS 64-bit, 32-bit

        - Debian 6.0 64-bit, 32-bit
        - Debian 5.0 64-bit, 32-bit

        - Fedora 9 64-bit (untested but paths checked with distro rpms)
        - Fedora 8 64-bit (untested but paths checked with distro rpms)

  Moved clang-builtin include dir position to immediately precede /usr/include,
  matching gcc compiler. Fixes #include_next shenanigans that lead to failures
  when clang++ is used to compile source with <cstddef>. libstdc++ versions
  4.3.0, 4.3.1 and 4.3.2 are at issue, which ship bundled on Debian 5.04,
  Ubuntu 8.10 and Fedora 10. Example error from Ubuntu 8.10:

hsearch0.patch (10.2 KB)

Not sure if I can approve the patch, but I like it a lot. Probably as
good as it gets until we manage to factor this in a config file or
something (and select the default at configure time).


Seems ok to me, please apply, thanks!