- Modified the synchronization mechanism to use synchronized keyword
  - Removed takeCount, which was incorrectly made static for each class,
and replaced with a boolean taken per instance
  - Added checkParameters method to test if all JNI arguments are
available before calling the operation. This is necessary to separate
the cause of RuntimeException and be able to call taken in the finally
clause after calling the operation.
  - Removed support for constructors; they are not compatible with
take/free management. Previous implementations was not thread-safe when
constructors were involved.