Get rid of deprecated QSignalMapper
Summary: QSignalMapper class is obsolete. This patch replaces its occurrences with lambdas. Qt version upgrade to 5.6 is needed because addAction overload has been added in Qt 5.6
Test Plan:
- Start User Menu editor with "LaTeX -> Edit User Menu". Try to add some items using popup menu.
- Create a project and use sidebar popup menu to handle its components.
- Open some structured document and use the "Structure" panel to manage the structure items.
Reviewers: Kile, mludwig
Reviewed By: Kile, mludwig
Tags: Kile
Differential Revision: https://phabricator.kde.org/D23616