GENERAL NOTES
* g++ seems to require that /usr/include/atm.h has definitions BEGIN_DECLS
  and END_DECLS in it for proper linkage. Otherwise error messages
  complain about undefined reference to text2atm.
* gcc on the other hand works fine without them.

ABOUT USAGE
* SAP is defined 100 in the code, it is not possible to define it using a
  command line argument.
* the user is prompted for data to send.