updated libraries

[Luiz Henrique de Figueiredo <lhf@...>]

A new version of MAPM has just come out and I have updated my mapm library.
The main change is that lmapm now accepts optional number of digits for results
in many functions and the buffers for converting numbers to strings are now
dynamically allocated.

I have also updated the bc, alarm, and gdbm libraries with minor changes.
They are available at
        http://www.tecgraf.puc-rio.br/~lhf/ftp/lua/

Enjoy.
--lhf