Rules to migrate GRASS 5.0 modules into GRASS 5.7

While implementing GRASS 5.7 a major cleanup of GRASS modules
has to be done. The following rules shall help the programmer
to migrate a 5.0 module into the 5.7 environment.


1. Add GPL statement

2. Programming details:
   o String buffer length:
     - to be identical for all modules
   o consistent return types. Situation in 5.0:
     The majority of functions return 0 on error and 1 on success, but there
     are many which return 0 on success and a negative value on failure.
     Proposal for 5.7? see below

   o Copying input parameters into a buffer, i.e.:

	strcpy (name, option.input->answer);
	strcpy (result, option.output->answer);

      is usually unnecessary. Furthermore, it's something which should be
      discouraged, due to the usual problems with fixed-size buffers.

   o Pre-formatting error/warning messages, e.g.:

        if (mapset == NULL)
        {
                char buf[200];
                sprintf (buf, "cell file [%s] not found", name);
                G_fatal_error (buf);
        }

        is unnecessary, as G_fatal_error() and G_warning() already do this,
        e.g.

        if (!mapset)
                G_fatal_error("cell file [%s] not found", name);

   o Ideally, all abnormal exits would be via G_fatal_error(), rather
     than calling exit() directly.

   o The value passed to exit() should be non-negative. exit(-1) is just
     a confusing way of writing exit(255).

   o C++ style comments are forbidden for portability reasons:
     use /* comment */ but NOT //comment

3. Style of file: We can reach pretty indenting through:
    indent -i4 -npsl -di0 -br -nce -d0 -cli0 -npcs -nfc1 FILE.c
   This should be done before uploading.

... to be extended...
