The existing code allocated 2 bytes (char*), but gtty() needs 6 bytes
(struct sgttyb), so isatty() smashed the stack and corrupted its
return address, probably causing SIGBUS or SIGSEGV.
Fix by switching to TIOCGETD, which needs 2 bytes. TIOCGETD isn't in
the manual for tty(4), but does appear in
https://minnie.tuhs.org//cgi-bin/utree.pl?file=V7/usr/sys/dev/tty.c
This fixes hilo_c.pdpv7 and hilo_mod.pdpv7 in simh-pdp11.
Change the alignment in C structs (wa, pa, sa, and so on) from 1 to 2
bytes. This prevents the SIGBUS when PDP-11 Unix V7 catches the
misalignment. This fixes hilo_p.pdpv7 in simh-pdp11.
Change ALIGN to document that sections have 2-byte alignment. This
change should have no effect, because the sections only contain 2-byte
values.
