Run 'gofmt -s' over everything

I didn't previously know about 'gofmt -s' but I definitely want what it
does for me.
sinksmtp: support \\ in quoted strings to escape backslashes

You don't need to do this unless the backslash preceeds a ", but let's
support it just in case. cmd/rlex_test.go gets some improved comments
too.
sinksmtp: more and better comments on tests

These are always called for.