CMake adjustments for building under Win32

This pull request contains many fixes by RPeschke and me to fix issue eudaq/eudaq#5;
Issue eudaq/eudaq#8 is also fixed.

This has been tested (main lib + gui) on Windows 7, 64bit, using MSVC 12, 32bit, Qt4.8, and the current version of pthreads-w32. RPeschke also tested the TLU producer.
Building under Linux (Ubuntu 12.10) still works.

The documentation (README.md) has been updated but the manual does not reflect the changes yet -- this should be fixed before the pull request is merged; I would like others to check and test these changes in the meantime.