port the RBT code to userland by making it part of libc.

src/lib/libc/gen/tree.c is a copy of src/sys/kern/subr_tree.c, but with
annotations for symbol visibility. changes to one should be reflected
in the other.

the malloc debug code that uses RB code is ported to RBT.

because libc provides the RBT code, procmap doesn't have to reach into
the kernel and build subr_tree.c itself now.

mild enthusiasm from many
ok guenther@

procmap fumbles with uvm_map_addr structures, which are now in RBTs

it also does proper traversal of the tree (ie, it does FOREACH)
which in turn uses MIN and NEXT operations to iterate over the whole
tree. theyre complicated and need code.

so for now this pulls in subr_tree.c from the kernel and builds it
as part of procmap. that allows for traversal of the RBT using the
same code that the kernel uses.

it is a bit ugly though because procmap updates the pointers between
items in the tree so they point at local copies instead of kernel
addresses. its made worse because RBT code has pointers between
rb_entry structs, not between the nodes.

im putting this in now to unbreak the tree. it can be polished after
coffee/naps.

Since the "better kmem pointer hiding" commit, procmap does not work
anymore for regular users.
So remove the setgid kmem for the time being (until tedu@ fixes it).

ok tedu@

bogus leftover SRCS line

supposed to use cflags, oops

Wall

rough cut of netbsd's pmap process memory map inspector.
initially from drahn@, renamed to procmap to avoid conflict with
unrelated pmap(9).
works more or less as advertised, could definitely use some work though.
would be really nice if somebody made it use sysctl and not kmem.
more or less ok deraadt@ drahn@