Mainly focus on files that use BSD 3-Clause license.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.

Even though _Static_assert() is pretty robust for C code, it cannot work
correctly with C++ code.  This is due to the fact that C++ template
parameters may contain commas that are not enclosed in parentheses. For
example:

	static_assert(foo<int, int>::bar == baz, "...");

This causes _Static_assert to be called with an excessive number of
parameters.  If you want to use static_assert in C++, just use a C++11
compiler.

Reported on:	current@, ports@

__assert() is called when an assertion fails. After printing an error
message, it will call abort(). abort() never returns, hence it has the
__dead2 attribute. Also add this attribute to __assert().

MFC after:	3 weeks

Add a few $FreeBSD$

specifically allow changes to the NDEBUG macro between #includes of assert.h

# This appears to not break X11, but I'm having problems compiling the
# glide part of the server with or without this patch, so I can't tell
# for sure.

Reviewed by:	asmodai, bde

Change assert() macro to print failing function name.
Change K&R function prototype wrapper to ANSI prototype.
This makes us C99 conforming.