Libraries found by CMake modules are usually handled with their full
path. This makes linking against those libraries a lot more robust when
it comes to libraries in non-standard locations, as otherwise we might
mix up libraries from different locations when link directories are
given.

One excemption are libraries found by PKG_CHECK_MODULES. Instead of
returning libraries with their complete path, it will return the
variable names as well as a set of link directories. In case where
multiple sets of the same library are installed in different locations,
this can lead the compiler to link against the wrong libraries in the
end, when link directories of other dependencies are added.

To fix this shortcoming, we need to manually resolve library paths
returned by CMake against their respective library directories. This is
an easy task to do with `FIND_LIBRARY`.

Move the odd code that provides a hierarchical display for projects
within the IDEs to its own module.

Move the nanosecond detection in time structures to its own module.

Since OpenSSL isn't used any more on OS X, there is no dependency
on any MacPorts library under /opt/local and there is no danger of
conflicts between MacPorts and system iconv. For this reason the
system iconv can always be used now.

As an alternative to OpenSSL when we're on OS X. This one can actually
take advantage of stacking the streams.

We don't really need our own module to find libssh2. Using pkg-config
lets the standard tool do the work for us and let us fit more naturally
in the workflow as we respect the pkg-config search paths.