* contrib/hbct/hbct.hbp
* contrib/hbwin/hbwin.hbp
* contrib/xhb/xhb.hbp
+ install .h headers to contrib dir only (and not anymore to
the central Harbour include dir). This means that 3rd party
or user code that uses these C-level contrib headers will now have
to add contrib package using <contrib>.hbc hbmk2 option instead
of manual -l options. INCOMPATIBLE.