[Releasing] 5.6.0 build error fixes

[Thiago Macieira]

Hello

I spent two hours building Qt and filed the following fixes for failures to 
build from source. I consider FTBFS problems to be P0, so I submitted all fixes 
to 5.6.0:

https://codereview.qt-project.org/151164
https://codereview.qt-project.org/151170
https://codereview.qt-project.org/151171
https://codereview.qt-project.org/151173
https://codereview.qt-project.org/151176
https://codereview.qt-project.org/151177 (backport from a 5.6 commit)

Plus the qtserialbus issues, which are resolved by removing it entirely from 
the build.

As explained, I am extremely busy for the next couple of weeks, so I will not 
monitor those changes for comments or +2. If there is need for fixing the 
changes, please do them without waiting for me.

Don't wait for me to stage either.
-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center