Make LDOWN take priority over caption-less drag

Again.

Fixes #3940
Revert recent changes to mouse wheel handling

This reverts commit 8d3ad50708f56c61a243b8b953c8eb4ca2ace8b7.
This reverts commit 4ff7ba5771b6349ce23edb651a9051fff5f67d48.
Silence possible loss of data warning
SSATag: Initialize all member variables in the constructor.
GaussianKernel: Remove the default copy constructor.

We don't need it and using it would lead to double delete.
Enable C++11 explicit deletion of copy constructors now that we use VS2013.