Initial import of filescan source
Add check rule to Makefile; runs clang static analyser
Improve line-handling logic in hexdump_region. Numerous other changes.

* Logic in hexdump_region is now more sane; there is less repetition of
  code.
* Conditionals no longer have spaces inside the brackets.
Merge existing Git repo. into the one GitHub created.

Doing so preserves the LICENSE, README.md and .gitignore files that were
populated by GitHub