Support for FreeBSD

We update the scripts to use `/bin/sh` instead of bash.  Also, a
small update to `CMakeLists.txt` is included for making debugging
a little easier.
Support the Tilera platform

This patch provides build and test script updates for the Tilera
platform.  The cmake scripts autodetect if you are configuring on a
system with a Tilera MDE installed, so you can use the normal `cmake`
command in a build directory with standard cmake options.  Note that
we turn off building the documentation on Tilera, even if Sphinx is
installed.

The major modification to our standard workflow is testing: replace
`make test` with `./tile-test`.  This assumes there is a working
connection to a Tilera device.

Installation requires sudo access, i.e., `sudo make install`. If you
intend to use these files regularly, then you should use an installation
prefix that includes `$TILERA_ROOT/tile`.  One good example is
`$TILERA_ROOT/tile/usr/local`, but you can use any directory you want
that is supported by the various `tile-monitor` upload and mount options.
Merge branch 'feature/freebsd' into c-template

* feature/freebsd:
  Support for FreeBSD
Merge remote-tracking branch 'template/c-template' into feature/tilera
Use BSD compatible yield function

BSD uses the same `sched_yield` function as Linux, so we need to
include the macro definition to use it in libvrt/yield.c.
Include threads package

In an earlier commit, the threads package was removed from our
cmake lists file. However, this generates a linker error so we
put it back in.
Merge branch 'feature/tilera' into develop

* feature/tilera:
  Include threads package
  Use BSD compatible yield function
  Support the Tilera platform
  Support for FreeBSD