Update gnulib and convert .cvsignore to .bzrignore.

        * gnulib: Update.
        * .bzrignore: Add.
        * .cvsignore: Remove.
        * contrib/.cvsignore: Likewise.
        * doc/.cvsignore: Likewise.
        * man/.cvsignore: Likewise.
        * po/.cvsignore: Likewise.
        * src/.cvsignore: Likewise.
        * tests/.cvsignore: Likewise.
        * build/mkinstalldirs: Remove: no longer needed.
        * po: Update.