Patch to fix Stability issues and memory leaks on hash keys

Hash seems to keep a pointer to the keys of the elements it stores.Right now that memory is managed by the caller of the method... In some cases it causes a memory leak, but as the key memory is external to the hash it is a potential segfault (I think this could be related to other existing segfaults which are difficult to identify)

I proposed a patch to create a copy of the key for the hash to use (the hash releases that memory automatically when freed)...

I looked trough all the code to correct the calls to axutil_hash_set() in order to unify the memory management, and runned all the samples to check it worked correctly (I know hash it's used in a lot of places)

Please review the patch to see if any changes need to be done on it...