Reorganize the way jump_target_hash is stored in the JIT. Free entries in jump_target_hash which point inside a dynamic method when it is freed. Fixes #669815.
Fix arm thunk creation in dynamic methods. Fixes #673828.

Conflicts:
	mono/mini/mini.c
Implement GHashTable iterators.
Merge pull request #155 from Unity-Technologies/fix_arm_thunk

Fix arm thunk