Convert code to use FSmallocarray() & FSreallocarray()

Provides automatic integer overflow checking in allocation size calculations
(Though we already have explicit checks before using values provided
 over the protocol in calculations, so many were already manually checked.)

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
6 jobs for reallocarray in 1 minute and 40 seconds (queued for 1 second)