Export the whole thread name in kinfo_proc

Export the whole thread name in kinfo_proc

kinfo_proc::ki_tdname is three characters shorter than
thread::td_name.  Add a ki_moretdname field for these three
extra characters.  Add the new field to kinfo_proc32, as well.
Update all in-tree consumers to read the new field and assemble
the full name, except for lldb's HostThreadFreeBSD.cpp, which
I will handle separately.  Bump __FreeBSD_version.

Reviewed by:	kib
MFC after:	1 week
Relnotes:	yes
Sponsored by:	Dell EMC
Differential Revision:	https://reviews.freebsd.org/D8722