Use QString::toLatin1() rather than ::toAscii()

The toAscii (and fromAscii) are removed from Qt5 in favor of Latin1.
Implement tempfile support for Qt5
Implement standard directory support for Qt5
Implement drag/drop properties for Qt5
Prevent unused variable warnings
Port QSKIP semantics over for Qt5
Port plugin exporting to Qt5
Set -fPIC for static libraries

Qt5 doesn't work without -fPIC.
Disable -D_FORTIFY_SOURCE=2 in Debug mode

Qt5 doesn't support it in Debug builds.
Use QtWidgets for headers which moved