MFC r316549,r316550,r316551,r316554:

MFC r316549,r316550,r316551,r316554:

r316549:

Add sys/types.h #include to EXAMPLE to provide a complete functional
standalone example program

r316550:

sbuf(9): convert SYNOPSIS section from .Fn entries to .Fo/.Fa/.Fc entries

This shortens the column count on many lines considerably.

While here, add "(void)" to sbuf_new_auto(3) for consistency with style(9)
recommendations.

r316551:

sbuf(9): clarify kernel-only APIs

- move sbuf_bcopyin(9) and sbuf_copyin(9) near sbuf_new_for_sysctl(9), as
  all three functions are kernel-only APIs.
- add #ifdef _KERNEL around sbuf_*copyin and sbuf_new_for_sysctl(9) to
  make it visually clear that they are kernel-only APIs.

r316554:

sbuf(9): add MLINKS for sbuf_{clear,get,set}_flags(9)

These functions were added in r279992.

git-svn-id: svn://svn.freebsd.org/base/stable/10@321115 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f