Slider Dialog changes

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@27121 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
#3144 fix and code cleanup for [27119]

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@27122 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Do not ignore mouse down on Windows

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@27123 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e