MFC r271975:
Improvements to asmc(4):

1. changed the code so that 2**16 keys are supported
2. changed the number of possible fans in a system from 2 to 6
3. added write support for some fan sysctls
4. added a new sysctl which shows the ID of the fan
5. added four more apple models with their temperature keys
6. changed the maxnumber of temperature keys from 36 to 80
7. replaced several fixed buf sizes to sizeof buf

Obtained from:	     Denis Ahrens denis at h3q.com
MFC r273733, r273740 and r273773:

The SYSCTL data pointers can come from userspace and must not be
directly accessed. Although this will work on some platforms, it can
throw an exception if the pointer is invalid and then panic the kernel.

Sponsored by:	Mellanox Technologies