Various fixes for LP64

Changes include
- Cast numbers to their proper length before casting to a pointer.
- Use intptr_t when pointers are stored as integers.
- Eliminate 'implicit declaration' warnings

Signed-off-by: Matthew Leach <matthew.leach@arm.com>
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>

Change-Id: I5664a087c5fbc322baa9178552404dbe9a992359