C Shells do not free memory; (correction)

[Jay Lepreau]

I dun forgot: as 4.2 was distributed csh used its own alloc.c, which is
the old one, and of course does exhibit that nasty behavior after
awhile.  I had changed it here to use a modification of the standard
libc one.  Get rid of stdio, add support for the "alloc" builtin (use
the mstats routine) and one surprise: remove the ASSERT for freeing a
free block at the beginning of free().  Turns out csh does exactly that
when processing the =~ and !~ operators, and if you look real close
you'll discover that check is commented out in the original alloc.c.

Jay Lepreau