statistics: make selection keyboard modifiers more general

Up to now, we passed a "shiftPressed" flag to the individual
selection functions. To be more general replace by a struct
with "shift" and "ctrl" flags.

While doing this:
1) Move the struct into a new statsselection file for better
   encapsulation.
2) Change shift to control in the scatter series, since individual
   selection of items is usually done with control, not shift.
   Shift usually means "select range".

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

1 files changed, 2 insertions, 0 deletions

diff --git a/stats/statsselection.cpp b/stats/statsselection.cpp
new file mode 100644
index 000000000..38bbd7f8b
--- /dev/null
+++ b/stats/statsselection.cpp
@@ -0,0 +1,2 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "statsselection.h"