AArch64: Use of long for pointers in PropertyValuesHolder

Long is used in PropertyValuesHolder class to store native pointers
as they can be 64-bit. Note that jmethodID, a pointer to structures,
is also carried in long rather than int to support 64-bit system.

Change-Id: Ifb514fc8473d7c41c0d6194fc6eb85d4816b2cd9
Signed-off-by: Marcus Oakland <marcus.oakland@arm.com>
Signed-off-by: Ashok Bhat <ashok.bhat@arm.com>