* Add prototype for vfscanf to <stdio.h>.
* Remove #define of vfscanf to __svfscanf from <stdio.h>.
* Include local.h in libc files which need __svfscanf.
* Add vfscanf weak alias to __svfscanf.
Fixes standards/16997.
NOTE: libc minor not bumped -- ride on the bump to 12.84 made by
itojun today.