Java bindings in Open MPI support Java arrays and direct buffers
as buffers. All non-blocking methods must use direct buffers and
only blocking methods can choose between Java arrays and
direct buffers.
Though Comm.allToAllw() is a blocking method, Java applications
using Java arrays as buffers get compilation errors.
This fix enables using Java arrays in Comm.allToAllw().
Signed-off-by: Kurita, Takehiro <fj6370fp@aa.jp.fujitsu.com>