#13 Convert to Qt5

[Chris Mayo]

Qt 4 is deprecated, first patch attached is a straightforward switch to Qt5.

This still wouldn't build for me because I had LDFLAGS set and the .pro files are incorrectly using QMAKE_LIBS instead of QMAKE_LFLAGS. Therefore the second patch attached. N.B. I also stripped out the hard coded values for QMAKE_CXXFLAGS and QMAKE_CFLAGS.

Tested on Gentoo amd64.