stats.7: fix nonexistent references, various lint issues

[yuripv]

Summary

Fix various issues reported by mandoc lint:

mandoc: /data/src/freebsd-git/base/share/man/man7/stats.7:89:2: ERROR: inserting missing end of block: Sh breaks Bl
mandoc: /data/src/freebsd-git/base/share/man/man7/stats.7:109:15: STYLE: no blank before trailing delimiter: Xr ... 1,
mandoc: /data/src/freebsd-git/base/share/man/man7/stats.7:93:2: WARNING: unusual Xr order: btsockstat(1) after intro(8)
mandoc: /data/src/freebsd-git/base/share/man/man7/stats.7:95:2: WARNING: unusual Xr order: fstat(1) after ctlstat(8)
mandoc: /data/src/freebsd-git/base/share/man/man7/stats.7:102:2: WARNING: unusual Xr order: lockstat(1) after kldstat(8)
mandoc: /data/src/freebsd-git/base/share/man/man7/stats.7:104:2: WARNING: unusual Xr order: netstat(1) after mailstats(8)
mandoc: /data/src/freebsd-git/base/share/man/man7/stats.7:107:2: WARNING: unusual Xr order: procstat(1) after pmcstat(8)
mandoc: /data/src/freebsd-git/base/share/man/man7/stats.7:109:2: WARNING: unusual Xr order: sockstat(1,) after pstat(8)
mandoc: /data/src/freebsd-git/base/share/man/man7/stats.7:110:2: WARNING: unusual Xr punctuation: none before stat(1)
mandoc: /data/src/freebsd-git/base/share/man/man7/stats.7:110:2: WARNING: unusual Xr order: stat(1) after sockstat(1,)
mandoc: /data/src/freebsd-git/base/share/man/man7/stats.7:113:20: WARNING: unusual Xr punctuation: , after zpool-iostat(8)
mandoc: /data/src/freebsd-git/base/share/man/man7/stats.7:109:6: STYLE: referenced manual not found: Xr sockstat 1,
mandoc: /data/src/freebsd-git/base/share/man/man7/stats.7:113:6: STYLE: referenced manual not found: Xr zpool-iostat 8

[debdrup]

I thought I had run lint, but you've pretty much proved I didn't. My apologies, and deep thanks.

This looks excellent to me! :)

[bjk]

I expect I should be the one committing this?
But I will hold off for a bit in case someone wants to respond to the 'kldstat' remark.

share/man/man7/stats.7

109

Not directly part of this change, but kldstat claims to "display status of dynamic kernel linker", which is not exactly a "statistics" thing in my mind.

[yuripv]

In D25166#554560, @bjk wrote:

I expect I should be the one committing this?
But I will hold off for a bit in case someone wants to respond to the 'kldstat' remark.

I can commit this, and we can sort out kldstat separately? (I'm just cleaning up the nonexistent .Xr a bit.)

[bjk]

Okay, please go ahead.