avoid C-style cast warnings from GCC for wait-related macros * lo-utils.h (octave_wait): New class. * lo-cutils.h, lo-cutils.c (octave_wifexited, octave_wexitstatus, octave_wifsignaled, octave_wtermsig, octave_wcoredump, octave_wifstopped, octave_wstopsig, octave_wifcontinued): New functions. * toplev.cc, pager.cc, syscalls.cc: Use octave_wait functions instead of WIFEXITED, WEXITSTATUS, WIFSIGNALED, WTERMSIG, WCOREDUMP, WIFSTOPPED, WSTOPSIG, WIFCONTINUED macros.