Various on qt4-mac

[Michael Dickens]

OK.  So, my changes to qt4-* will hopefully be:

* Upgrading qt4-* to use 'select' since that seems to be the best way to
allow the user to easily move between various installed versions.  So,
I'm creating a 'qt4_select' port to handle this need, copied from
'python_select' & modified for qt4's needs.

* Upgrading qt4-mac-devel to 4.7b1, assuming it proves relatively simple
to do (Qt claims it should be).

* Upgrading qt4-x11 to 4.6.3.

* Creating qt4-x11-devel to mirror qt4-mac-devel.

* Not going to do variants for debug or release, just leaving that as is
& doing combined, as before.  BUT: Because I'm moving to using 'select'
all of the regular and debug .pc files will be installed and available
for use.  Otherwise, what is installed and where it is installed will
remain the same (per selecting it).

* Moving to using compiler.cpath and compiler.library_path, and even
better: moving ${prefix}/include to the end of the path list so that it
comes last in any search.  This last change should take care of
build-time conflicts with at least some other ports (hopefully most or
all); in initial testing 'libevent' no longer conflicts (I don't have
the other known conflicting ports installed, but I'll try installing
them to see if they still conflict).

All of the above should take a few days to create and test -- wishing
Qt4 didn't take so !@#$ long to compile & be ready for destroot, but
I'll make do. - MLD