Uninstall old version on update
* src/inst-gpg4win.nsi (CheckExistingVersion): Remove message boxes. * src/installer.nsi: Call uninstaller of old version if neccessary. * src/uninst-gnupg-w32.nsi: Fix waiting for the uninstaller.
The messages provided no real information or choices. Uninstalling
is also cleaner then the usual case of overwriting.