MFC r324311: sysctl-s in a module should be accessible only when the module is initialized

Sponsored by: Panzura

MFC r298931, r298981, r299375:

Minor spelling fixes in:
sys/dev, sys/sys

Many of these have user-visible strings.

MFC r263710, r273377, r273378, r273423 and r273455:

- De-vnet hash sizes and hash masks.
- Fix multiple issues related to arguments passed to SYSCTL macros.

Sponsored by: Mellanox Technologies

Partial MFC of r267961, r267973, r267985, r267992, r267993 and r268005:
Backport some macro definitions to make backporting code from FreeBSD
current easier.

Merge 261595: simplify the SYSCTL_COUNTER_U64() macro.

Merge 261593 from head:
Provide macros that allow easily export uma(9) zone limits and
current usage via sysctl(9).

MFC r258661:
Add sysctl KERN_PROC_SIGTRAMP to retrieve signal trampoline location for the
given process.

Approved by: re (gjb)

MFC r263710, r273377, r273378, r273423 and r273455:

- De-vnet hash sizes and hash masks.
- Fix multiple issues related to arguments passed to SYSCTL macros.

Sponsored by: Mellanox Technologies

Partial MFC of r267961, r267973, r267985, r267992, r267993 and r268005:
Backport some macro definitions to make backporting code from FreeBSD
current easier.

Merge 261595: simplify the SYSCTL_COUNTER_U64() macro.

Merge 261593 from head:
Provide macros that allow easily export uma(9) zone limits and
current usage via sysctl(9).

MFC r258661:
Add sysctl KERN_PROC_SIGTRAMP to retrieve signal trampoline location for the
given process.

Approved by: re (gjb)