Add Compiler flag `-fPIC`
This fixes an issue on `x86_64` machines where linking to `libaxe.a` would throw
```
relocation R_X86_64_32S against `.rodata' can not be used when making a shared object; recompile with -fPIC
```
Moved debugging define to above where it is 1st used in JIT.cpp
Added methods to add and remove threads from the RunableQueue
- Added functions in axe.cpp and changed the header to suit
- Moved the contains function of runable queue to public
- Added option to enable tracing in axeCreateInstance too.