Add update handling to installer and uninstaller
* src/gpg4win.nsi (is_update): New var. * src/inst-gpg4win.nsi (SEC_gpg4win): Call uninstaller with is_update. * src/inst-sections.nsi (SEC_gpa, SEC_kleopatra): Handle desktop links depending on update. * src/installer-finish.nsi: Don't delete desktop links on update. * src/installer.nsi: Parse is update variable from cmd line.
For now this only adds proper Desktop shortcut handling. If
a user has explicitly deleted a desktop shortcut of Kleopatra
or GPA it does not add another one on update.
But in the future we could probably do more things differently
- GnuPG-Bug-Id: T3729