array of ARG_MAX size. ARG_MAX is currently 256k, which causes a rather
serious stack overflow (kernel stacks are not very large, usually 8k).
Fixes memory corruption problems observed after accessig /proc/1/cmdline
during tests. Problem in my case manifested itself as massive lossage
in ffs_sync(), resulting in a crash, and sometimes, pooched file systems.
XXX This could, and probably should, be rewritten to use a much smaller
temporary buffer, and a loop around uiomove().