GitLab

Switch from simple typecasts to conversion functions for the objects
passed in and out of JNI calls.  No real change here; object references
are still just pointers.

Use explicit pin/unpin calls for primitive arrays.  For GetStringChars
we now pin the char[] rather than the String object.  (Which doesn't
make much difference in the grand scheme of things, since you need to
keep the String to pass into the release function anyway.)