Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Fix whitespace inconsistencies found in homegrown Symbol.maps.

Fix various whitespace inconsistencies in sys/teken.

mdoc: reorder sections consistently

Add proper build infrastructure for teken.

I'm not sure whether we should install teken as a library on any stock
FreeBSD installation, but I can imagine people want to tinker around
with it now and then. Create a /sys/teken/libteken, which holds a
Makefile to install a shared library version of the terminal emulator,
complete with a manpage.

Also add Makefiles for the demo/stress applications, to build it against
the shared library.