GNU APL build system changes

[Dr . Jürgen Sauermann]

    Hi,
      
      as some of you have noticed, I made some changes to the GNU APL
      build system.
      
      Some of these changes were simplifications of the build system
      (some automatically
      generated .cc and .hh files like configure_args.cc are
      gone for good), while other changes
       were needed to support Autoconf VPATH builds. Also all files
      generated by ./configure
      now stored in the top-level directory so that the subdirectory src
      (which is shared by all
      VPATH builds) is no longer muddied with ./configure results.
      
      The purpose of VPATH builds is to be able to build several
      ./configure variants in
      parallel. Different VPATH builds are needed to discover build
      problems, in particular with
      rarely used ./configure variants before these problems  are
      committed to the savannah
      SVN server.
      
      There could still be glitches in the new build structure, so
      please keep reporting
      them.
      
      SVN 1449.
      
      Best Regards,
      Jürgen