Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Implement ifconfig_wlanX="HOSTAP".

Not only this is a bit cleaner, it allows multiple instances of hostapd to be
running on the system host, useful for simultaneous dual-band WiFi.
This is similar to ifconfig_wlanX="WPA" but it uses /etc/hostapd-wlanX.conf.
Compatibility with hostapd_enable=YES/NO was kept.

Reviewed by: adrian

Prepare for the removal of set_rcvar() by changing the rcvar=
assignments to the literal values it would have returned.

The concept of set_rcvar() was nice in theory, but the forks
it creates are a drag on the startup process, which is especially
noticeable on slower systems, such as embedded ones.

During the discussion on freebsd-rc@ a preference was expressed for
using ${name}_enable instead of the literal values. However the
code portability concept doesn't really apply since there are so
many other places where the literal name has to be searched for
and replaced. Also, using the literal value is also a tiny bit
faster than dereferencing the variables, and every little bit helps.

As previously discussed, add the svn:executable property to all scripts

rc support for vaps

Add reload functionality.

PR: conf/116659
Approved by: sam, erwin (mentor)

- Add a startup script for hostapd.
- Document associated variable in rc.conf(5).

Approved by: dougb
MFC after: 1 week