Fix r264346 for ia64. We need to allocate memory for the function
descriptors in order to relocate RTLD itself. To allocate memory,
we need the pagesizes array initialized, but that happens after
RTLD is relocated. This ordering is important for amd64, but it's
opposite of what ia64 needs. Handle this conflict with the define
called RTLD_INIT_PAGESIZES_EARLY. When defined, obtain the page
sizes before relocating rtld, otherwise do it after.
Improve the KTR logs by naming the values.
Drop KTR records when we're in the debugger so that the debugger isn't
changing or overwriting the trace buffer. When KTR is enabled for things
like traps or pmap functions, the amount of logging can be substantial.
Improve markup, change references to nonexistent vt_vga(4), remove some
language redundancy, and move the examples so sections are in the
standard order.

MFC after:	1 week