Fixed bugs + changed make file +
Fixed bug with the SetPrimitive of spawnWithArgument.
Added code for garbage collection barrier.
Fixed some bugs.
Some asserts added in search of bug.
Add and remove interpreters changed as the interpreters are now stored in a vector.
Changed the join method to allow a garbage collection to take place when the thread waits for a join to happen.
Changed the implementation of printString so that only one thread at a time can output to the console.
Added GC code for when a thread reaches a safe point.
Made allocation of objects thread safe.
Added a barrier for the garbage collection with methods to  support this barrier.
Added markInterpretersFrameAndThread method.
Rest of changes.