Apply much of Ilya's microperl patch, but instead of

Apply much of Ilya's microperl patch, but instead of
implementing the opendir()/readdir()/closedir() using
external commands give up "ANSI-pureness" and define them
in uconfig.sh, also define other stuff like rename() and putenv().
Leave out the $| emulation in my_fork() since we are
not supposed to have fork() under microperl.

p4raw-id: //depot/perl@20646