Force all source code to UTF-8 encoding by default

Force all source code to UTF-8 encoding by default

To keep things simple we should use a single character encoding
for all of our source files, and UTF-8 is the best choice as it
will handle any possible Unicode character but the majority of
our source is plain 'ole ASCII.

We really want to support full Unicode in our sources so we can
setup Unicode test vectors, have translations which are usually
in the standard encoding, and correctly support author names in
source code copyright comments.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>