[Kst] Compiling Kst on Linux for Windows - cross-compile for Windows

[Peter Kümmel]

To compile Kst on Linux for Windows use the build-server script.
In the root of the kst source dir call

     ./cmake/travis.sh

First time the cross-tools will be downloaded from sourceforge
and unpacked into the /opt dir and you will be ask for your sudo password.

Then a build-folder starting with a underscore "_" is created on
the same level as the kst dir, one for the 32bit and one for the
64bit/Qt5 build.

When in travis.sh the 'versionstring' variable is defined a installer
is build and NSIS is needed:

	sudo apt-get install nsis

Without a 'versionstring' only ZIP files are generated.

Should work on not too old Ubuntu based 64bit Linux versions.

Peter