AArch64: Use long for pointers in VideoEditor classes

For storing pointers, long is used in VideoEditor
classes, as native pointers can be 64-bit.

In addition, some minor changes have been done
to conform with standard JNI practice (e.g. use
of jint instead of int in JNI function prototypes)

Change-Id: Ifff3a28f2ab6774ee89d31770ad63451c8726431
Signed-off-by: Ashok Bhat <ashok.bhat@arm.com>
Signed-off-by: Marcus Oakland <marcus.oakland@arm.com>
Signed-off-by: Kévin PETIT <kevin.petit@arm.com>