sip4, pyqt4: new packages (Python 2 only)

These packages a bit tricky to build, having them in the repo would be nice :-)

I could only test them on a 32bit system, though I don't expect any trouble in 64, since they are python extensions, for the most part.

I hope the PKGBUILD files are OK, I "borrowed some inspiration" from other packages.


PS: Thanks guys, MSYS2 is awesome!
PPS: AFAIK Python3 is only supported on PyQt5 and SIP5.