Bump stream positions to 64 bits on:

SvLockBytes::SetSize()
SvStream::SeekPos()
SvStream::SetSize()
SvStream::SetStreamSize()
SvStream::Seek()
SvStream::SeekRel()
SvStream::Tell()
SvStream::remainingSize()
SvStream::nActPos
SvStream::nBufFilePos

Change-Id: I0521fd60d31d1a33e5634cbf51dd42edc46ad919
TODO: adapt callers of Seek()/SeekRel()/Tell()/remainingSize()