Sometimes, there is the one-off occation when one needs to
pass a huge list in rc...
This change makes devenv track total memory consumption
of environment groups allowing them to grow up to 1MB in
size (including overhead).
(Before, only the variable size was restricted, but
not the amount of files being created).
The maximum value size of a single environment variable
is set to half of the total size, which allows the
occational large value. (But not many of them).
Because we track all memory consuption, it is also
now possible to create around 10k small environment
variales.
A hashtable is added for name lookups and the qid.path
was changed to allow direct indexing into the entry
array without needing a scan lookup.
All smalloc() calls have been removed, exhaustion is
handled with error(Enomem) avoiding deadlock
in case we run out of kernel memory.
when opening a /env file ORCLOSE, and the process exits, envgrp() would
return nil can crash in envremove() because procexit will have set up->egrp
to nil before calling closefgrp().
the solution is to capture the environment on open, keeping a reference in
Chan.aux, so it doesnt matter on what process the close happens and a
env chan will always refer to its original environment group.
