bintrans: Error out if writing to the output failed.

- Cover all code paths.
- When decoding, check all output files, not just the last one.
- A simple `ferror()` check is not enough as an error may later occur
while flushing whatever remains in the output buffer.

MFC after: 1 week
Sponsored by: Klara, Inc.
Reviewed by: allanjude
Differential Revision: https://reviews.freebsd.org/D43532

Remove copyright strings ifdef'd out

We've ifdef'd out the copyright strings for some time now. Go ahead and
remove the ifdefs. Plus whatever other detritis was left over from other
recent removals. These copyright strings are present in the comments and
are largely from CSRG's attempt at adding their copyright to every
binary file (which modern interpretations of the license doesn't
require).

Sponsored by: Netflix

usr.bin: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by: Netflix

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

Add the base64 command using b64encode and b64decode

Various scripts expect the base64 command to be present. We've had the
code and it's been exposed as b64encode/b64decode, but it wasn't widely
known under these names and the syntax is much different.

Reviewed by: delphij
Differential Revision: https://reviews.freebsd.org/D32945

bintrans: move files to a new directory

And reflect the change in various places.