relax SVN archive

Changed the memory allocation definition for the "curve_type" variable.

It was being defined by an equation involving itself...

Now, the definition assumes a maximum length of 20 characters. This will
be enough for all possibilities, e.g. "exp_2param_neg" has 14 characters,
and "exp_3param_inv_neg" has 18...

Maybe this will again change later.

Fix for the pymol.macro_write back end - the default file extension is now *.pml, not *.mac.

The file name is optional in the pymol.macro_write user function.

Updated the pymol.macro_write user function docstring.

Missing import of relax_io.open_read_file.

Fix for the molmol.macro_run user function GUI page.

The directory argument should have been None.

Fix for the results viewer window file opening.

The results viewer window can now open Molmol macro files.

The molmol macro files are no registered in the results file list as such.

They were previously registered as Grace files.

Bug fix for the molmol.macro_run and pymol.macro_run user function back ends.

The force flag does not exist.