Update Qt version

- New version (4.8.6) has important bugfixes, specially for MacOS X 10.9
Set build number to 0 because this is a new version
Fix compilation errors in Mac
Add patch to set the right ARCH flag for qmake in Mac

- Given that qmake is crucial to build Qt, it's better to compile it
with the right architecture.
- The patch was taken from the Qt MacPorts portfile
Merge pull request #131 from ccordoba12/update-qt

Update Qt version