Add descriptions to undocumented sysctls (hw, kern, vm)

[mhorne063_gmail.com]

Summary

An attempt to reduce the number of sysctls in the system that are missing descriptions.

I've taken some effort to examine each of the sysctls to determine their purpose, but due
to the range and quanitity of changes some descriptions may require additional detail. Input
is appreciated from anyone with relevant knowledge.

In addition to the grammar and functional accuracy of the descriptions added, there will
undoubtedly be some sysctls that I have missed. Please feel free to mention them in the
appropriate thread and I will add those descriptions.

This patch covers low level sysctls under hw, kern and vm.
Some of the areas touched by this patch:

• busdma (multiple archs)
• virtual memory
• sys/kern/
• sys/sparc64/
• sys/powerpc/
• sys/x86/local_apic
• geom

[kib]

sys/x86/x86/local_apic.c

205

This is indicator of the selected mode, not an enable switch. After that, I do not see any other way to say it other than "x2APIC mode", and now the description becomes useless.

209–210

Same there.

Also, the previous string was formatted stylish, Bruce wants the description to start on a new line always.

212–213

And there.

[mhorne063_gmail.com]

Updated some descriptions to match the desired style

[mhorne063_gmail.com]

sys/x86/x86/local_apic.c

205

I agree that the description becomes somewhat useless. However, I will keep it in simply for consistency and to reduce the possibility of confusion if a user were to think there was a greater explanation that was missing.