EMACS_GET_TTY_PGRP vs. emacs_get_tty_pgrp

[Ken Brown]

The macro EMACS_GET_TTY_PGRP defined in src/systty.h uses either 
tcgetpgrp or TIOCGPGRP to get the PGID of a terminal's foreground 
process group.  But src/process.c defines and uses its own 
emacs_get_tty_pgrp that only works on systems that have TIOCGPGRP.  Is 
there a good reason for this?  If not, I would like to try to prepare a 
patch to change process.c to use the macro instead.  This would simplify 
the code and would also extend some of the functionality in process.c to 
systems that have tcgetpgrp but not TIOCGPGRP.

Ken