Force 64 bit math in expr, from Daniel Verkamp
Upgrade modinfo to support multiple modules, and add tests, from Isaac Dunham.
Implement split.
Add xexit() and make error_exit() use it.
Typo fix
Misc website updates.
Test cases for split.
Add pivot_root.
Generate FLAG_longopt macros for --longopts with no corresponding short option.
Option type @ counts number of occurrences, it doesn't take an argument.
Implement mv as an extension of cp.
Patch that assumes that the presence of the string ".ko" indicates
use of a path to a module (*.ko.xz and similar included, but not supported).
Modinfo cleanups.

Don't use xopen() if you want to iterate through multiple files.
Don't abort if unable to open the file, but return error if it can't map it.
(And leak the filehandle.) All modinfo_file() actually uses is the filename,
no reason to go through dirtree() for that. Nothing is actually _checking_ the
return value of modinfo_file(). Avoid global data outside of toy_union.
Make sure extension is at end of file (we can add support for more extensions
later).