Fix Linux and CentOS compilation

[amyspark]

• Map between Qt package names and pkg-config names; fixes failed to build due qt5 #32
• thread.cpp: pthreads needed an additional parameter, my bad; fixes CentOS 7: pthread_setname_np issue #39

[wjakob]

I think the current code is correct for OSX and incorrect for Linux. They have different function signatures, which is a bit confusing.

[amyspark]

I've got it working on both MacOS and Linux Mint/Ubuntu (see https://github.com/amyspark/mitsuba/commits/add-license-and-readme). @chaosink, what errors did you get?

[chaosink]

Why not add , '-std=c++11', '-fPIC' to CXXFLAGS also in config-linux-gcc.py. 😄 Seems only the debug version is tested (I saw it on Travis CI), which is so slow.

Yes. This works on Linux Mint 18.2 for the debug version. For the release version, the two flags need to be added in config-linux-gcc.py.

Thanks for @amyspark .

[chaosink]

Maybe all the binaries can be put together, just like cmake did in 0.5.0 version.

[amyspark]

@chaosink 🤦‍♀️, I forgot to do it in #36... fix incoming.
As soon as this is merged, I'll add the release version configs to Appveyor and Travis too.

[diiigle]

confirmed: fixes compilation on Ubuntu (WSL).

[OstZ]

why not merge?