Make sure we can find the library in unit tests
cleanup frame processing and payload alignment

- remove a level of indentation making frame processing easier to read
- use qFromBigEndian(const uchar *src) to ensure alignment of payload size
rpath improvements

Improve on the previous commit adding QMAKE_RPATHDIR. We can now use
rpath for out-of-source builds, as well as on osx.
Merge remote-tracking branch 'other/master'

Conflicts:
	src/qamqpclient.cpp
	tests/tests.pri