[Gm2] change to compile and link command line switches

[Gaius Mulley]

Hi,

I've just checked in some changes which alter the behaviour of the gm2
front end so that it is similar to gcc.

So to compile only you can:

  gm2 -c foo.mod

to compile and link:

  gm2 foo.mod

If you really only want to link your program module then use:

  gm2 -fonlylink foo.mod

hopefully these changes will closer match new users expectations of the
gm2 front end

regards,
Gaius

   * gm2/lang-specs.h:  modified so that gm2 foo.mod will
     both compile and link file foo.mod.
   * gm2/lang.opt:  modified description of -fonlylink
     (removed internal usage).
   * gm2/gm2.texi:  changed compile commands in the
     hello world example to start with the simpler
     gm2 -g hello.mod.
   * gm2/gm2.texi:  replaced @filename with @file.
   * gm2/bnf/gm2m.bnf:  modified M2L to use -fonlylink.
   * gm2/examples/gravity/Makefile.in:  use -fonlylink.
   * gm2/examples/swig/exceptions/Makefile.in:  use -fonlylink.
   * gm2/examples/swig/strlib/Makefile.in:  use -fonlylink.
   * gm2/examples/swig/tiny/Makefile.in: use -fonlylink.