documentation/yocto-project-qs/yocto-project-qs.xml: Edits plus Matt Madison note...

documentation/yocto-project-qs/yocto-project-qs.xml: Edits plus Matt Madison note regarding older host systems

I made a few small edits and I added a reference to the
wiki page 'https://wiki.yoctoproject.org/wiki/BuildingOnRHEL4'
that has entries for older development hosts.  Right now all that
is there is the RHEL4 notes but the wiki page can be expanded as needed.

(From OE-Core rev: a23acbd48ee911d9882a78491280977fb62ea156)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>