Update CMakeLists

Update changelog

Changed version to v1.7.5-stable

Versioned to 1.7.4-rc8

Fixed "heads/" prepend problem for plugin upload deskflow#4695

Fixed tab indentation in ChangeLog

ChangeLog for v1.7.1-stable

ChangeLog for 1.7.0

Fixed client detected dialog not shown when Synergy is minimized desk…

…flow#4307

Suppressed empty server warning on startup deskflow#4240