InstallRules: try to fix MissingInstall test on VS6
Merge topic 'optional-install' into next

861742a InstallRules: try to fix MissingInstall test on VS6
InstallRules: added new variable to disable generation of install rules

The boolean variable CMAKE_SKIP_INSTALL_RULES
allows disabling generation of install rules for projects which don't
want them.
Merge topic 'optional-install' into next

be0458c InstallRules: added new variable to disable generation of install rules