fix typos in word "segment" and two additional typos in if_tl.c.

Fix some more uvm.h cleanup fallout.

uvmexp.ncolors being used where uvmexp.colormask wanted

- physmap_map, physmap_map_fini: pmap_update() must be performed before
freeing the VA; otherwise there is a window when it can be re-used while
stale TLB entries may be present.
- physmap_fill:

- physmap_map, physmap_map_fini: pmap_update() must be performed before
freeing the VA; otherwise there is a window when it can be re-used while
stale TLB entries may be present.
- physmap_fill: use MIN() instead of min(), since vsize_t is used.
- Add RCS ID comment while here and prevent physmap.h inclusion in userland.

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Contain support routines used to create and destroy lists of physical pages
from lists of pages or ranges of virtual address. By using these physical
maps, the kernel can avoid mapping physical I/O

Contain support routines used to create and destroy lists of physical pages
from lists of pages or ranges of virtual address. By using these physical
maps, the kernel can avoid mapping physical I/O in the kernel's address space
in most cases.

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