Add class to represent a probe ABI, and to find a matching one.
Empty stub of the probe ABI detector.

Apart from the dummy implementation (which is functionally equivalent to
the current behavior), we can't actually detect anything yet though, on
any platform.
Add convenience API to check if the Qt version is set.
Add caching of probe ABIs for QtCore DLLs.
Implement QtCore version detection for ELF, and detecting QtCore for a PID.

We currently have two ways of detecting the version:
- the file name
- the version printed when executing QtCore.so

For detecting QtCore for a given PID we only support /proc lookup at the
moment, a non-/proc fallback as we have it in the process list still needs
to be added.
Add architecture detection for ELF.
Add ldd-based detection of QtCore DLL used by a executable.
Start to use GammaRay::ProbeABI in the ProbeFinder API.
Add a method to get the absolute executable path, for ABI detection.
Run the probe ABI detection, if no ABI is specified explicitly.
Pick the best available probe.
Add operator== for GammaRay::ProbeABI.
Auto-detect the ABI when picking an executable on the launcher page.

Also use the nicer display names for the probe ABIs in the UI.
Find QtCore on Mac, using otool and lsof.
Add architecture detection for Mach-O files.
Refactor Mach-O parsing to prepare for reading load commands.
Read Mach-O load commands to obtain the QtCore version number.
Implement finding the used QtCore DLL for a given process id on Windows.
Implement architecture detection for a given QtCore DLL on Windows.
Add Qt version detection for Windows.