bug fix: generation of temporary file names for cached images should be
synchronized
version 1.2.24
Merge branch '1.2.x' into 1.3.x

Conflicts:
	freeplane/viewer-resources/version.properties
	freeplane_framework/windows-installer/Freeplane_without_Java.iss
	freeplane_framework/windows-portable/App/AppInfo/appinfo.ini