avoid memory issue with octave_vsnprintf * utils.h, utils.cc (octave_vsnprintf, octave_snprintf): Return std::string, not char *. (octave_vformat, octave_format): Return size_t, not int. (octave_vsnprintf): Simplify implementation with vasprintf. Include gnulib vasprintf.h from gnulib. * bootstrap.conf (gnulib_modules): Include vasprintf in the list.