Remove extraneous decls.
Add ``const'' to several places.
Allow ``make NOALIAS=1'' to remove IP aliasing.
Merge with OpenBSD - only the Makefiles vary.
We can now survive a compile with
-Wall -Wbad-function-cast -Wcast-align -Wcast-qual
-Winline -Wmissing-declarations -Wmissing-prototypes
-Wnested-externs -Wpointer-arith -Wredundant-decls
-Wshadow -Wstrict-prototypes -Wwrite-strings -Wchar-subscripts
(although the Makefile just contains -Wall).
allowing for a possible header on the front of all packets.
In OpenBSD, there's a structure containing the address
family here.
If we're building under OpenBSD, set up the ``flags'' part
of struct tuninfo (not there under FreeBSD) so that we config
the interface as POINTOPOINT.
Prefix prototypes with ``extern'' in os.c for consistency.
These changes are cosmetic under FreeBSD, but allow ppp to
build & work under OpenBSD (bar the srandomdev() stuff,
the inclusing of <net/if_var.h> and some Makefile symantecs).
