Correct some previous changes that would use the parser hash table in the vm
Change hash algorithm and remove mutex and vector members of ohashtable_t

  True atomicity cannot be guaranteed without an external mutex, due
to the way inplace operations are implemented, so, leave it for the
programmer to choose to use a global mutex if multiple threads store
state in a hash table; this also gives 20-30% speed improvement on
some tests with integer keys and values.
  Also switch to a well known simple but very efficient hashing
algorithm, djb2, that improves another 10% some stress tests:
http://www.cse.yorku.ca/~oz/hash.html
Change assertion to proper check of variable set to special internal type.

  Like some other special types, type check is only done when
storing the contents of a variable, and only invalid condition
allowed is assuaging null.