rev: coding style, various fixes

rev: coding style, various fixes

 * Change indentation to 8 characters and coding style, for better reading the code.

 * Add some memory allocation error handling.

 * Fix memory leaks. In cases when Ctrl-C is used to exit the program,
  'p' cannot be freed, so made it a global var, to share between main()
   and sig_handler(). Signal handing is necessary to fix some leaks, so
   added a very basic, non invasive, mechanism.

Signed-off-by: Davidlohr Bueso <dave@gnu.org>
Signed-off-by: Karel Zak <kzak@redhat.com>