This fixes various issues I found while trying to compile FSO in a cross
compilation setup using MinGW. This is a prerequisite for merging Tea-CI
support.
This should make it possible to have both DLL version installed at the
same time without causing conflicts.
Combined with the new DLL, this will finally fix#974.
Also adds code for detecting if the FreeTrack client is actually
reporting valid values. I only tested it with FaceTrackNoIR so it may
not work for other head trackers.
If "value" is empty, then attempting to access "value[value.length() - 1]" is equivalent to trying to access "value[-1]", which is an out-of-bounds access (causing debug builds to complain and undefined behavior).
Taylor Richards