MFC r267767:
Add FPU_KERN_KTHR flag to fpu_kern_enter(9).
Apply the flag to padlock(4) and aesni(4).
In aesni_cipher_process(), do not leak FPU context state on error.
MFC r267815:
Put the aesni_cipher_setup() and aesni_cipher_process() functions into
the file which is compiled with SSE disabled.
MFC r267768:
Add documentation for the fpu_kern(9) interfaces.

MFC r267785 (by brueffer):
Several small fixes.
MFC r267854:
Add fpu_kern.9 man page to the install.
MFC: r267978

In order to get vt(4) a bit closer to the feature set provided by sc(4),
implement options TERMINAL_{KERN,NORM}_ATTR. These are aliased to
SC_{KERNEL_CONS,NORM}_ATTR and like these latter, allow to change the
default colors of normal and kernel text respectively.
Note on the naming: Although affecting the output of vt(4), technically
kern/subr_terminal.c is primarily concerned with changing default colors
so it would be inconsistent to term these options VT_{KERN,NORM}_ATTR.
Actually, if the architecture and abstraction of terminal+teken+vt would
be perfect, dev/vt/* wouldn't be touched by this commit at all.

Reviewed by:	emaste
Sponsored by:	Bally Wulff Games & Entertainment GmbH