move opt_inet.h upwards, to enable VJC if INET is defined. if_ppp.c does not work without VJC.
move opt_inet.h upwards, to enable VJC if INET is defined.
if_ppp.c does not work without VJC.

MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame