tmpfs: allow shared file lookups

Tested by: pho


git-svn-id: svn+ssh://svn.freebsd.org/base/head@273430 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Take the lock shared in linker_search_symbol_name.

This helps sysctl kern.proc.stack.


git-svn-id: svn+ssh://svn.freebsd.org/base/head@273431 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Bump __FreeBSD_version to track SA-14:20, SA-14:21, SA-14:22,
SA-14:23

Approved by:	re (implicit)
Sponsored by:	The FreeBSD Foundation


git-svn-id: svn+ssh://svn.freebsd.org/base/head@273432 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f