Add --help and --version options to sampleimg
.gitignore: Ignore .dirstamp files
Add "subdir-objects" and "std-options" automake options
Move loader source files into format-specific subdirs
cmdlineparser.cc: Tweak "Try --help" message

Include a period at the end of the message.

Don't use backquote as "start quote" to match a single-quote "end
quote", as that usage seems discouraged these days; instead, just use
two single-quotes.
cmdlineparser.cc: Include "Try --help" msgs for many errors