Use explicity gpg4win libs in qt instead of -qt

* src/Makefile.am (gpg4win_pkg_qtbase_configure): Fix
passing -I and -L variables. Remove wrong device option
for pkg-config.
Switch zlib, libpng, libjpeg, freetype to our sources.
* src/inst-sections.nsi: Add install dependencies of the
libararies to qtbase, remove them from Okular and Kleop.
* configure.ac: Add dependencies for qtbase

This was a bit more difficult since an error in our quoting
of -I and -L variables made qt not look into our installation
directory and did not find the libraries.

But the advantage is that we no longer ship two potentially
different versions of the same library and have better control
over it through packages.common. Now only pcre remains as the
last used 3rdParty library from Qt.