* move system_revision.h to headers/private/libroot
* unify libroot's get_system_revision() (the one I introduced recently) with kernel's
get_haiku_revision(), the function is now called get_haiku_revision() in the kernel
and __get_haiku_revision() in libroot
* system_revision.c is now being built as part of libroot and as part of the kernel
* adjusted all callers of get_system_revision() accordingly
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@41516 a95241bf-73f2-0310-859d-f6bbb57e9c96
