Make monolite profile directory versioned (#4631)

Make monolite profile directory versioned (#4631)

If you're building with monolite currently the build system
checks for the existence of mcs/class/lib/monolite and just
uses it in that case.

It becomes a problem when bumping corlib version since if you
pull the update and try to build it'll use the old monolite
and you'll hit the "corlib version not in sync" error.

By making the monolite directory include the version this can
be avoided and everything works out of the box.

Also removed the confusing "You need Mono version 4.8 or better"
message since we actually require a newer version in
basic-profile-check.cs now and keeping them in sync is error prone.