We use a lot of lengths given to us over the network, so be more
paranoid about them causing an overflow as otherwise an attacker
might trick us in to overwriting other memory.
This primarily affects the client which often gets lengths from the
server, but there are also some scenarios where the server might
theoretically be vulnerable.
Issue found by Pavel Cheremushkin from Kaspersky Lab.
(cherry picked from commit 75e6e0653a)
Provides safety against them accidentally becoming negative because
of bugs in the calculations.
Also does the same to CharArray and friends as they were strongly
connection to the stream objects.
(cherry picked from commit 0943c006c7)
Pierre Ossman
Constantin Kaplinsky
Peter Åstrand