Source code was inconsistent on how they were referencing
include files in include/sane. In certain cases, sane/sane.h
and sane/saneopts.h was really including external copies (with
some preprocessor implementations anyways).
Updated backends with EXTRA_* files to allow Makefile's
to always pass in BACKEND_NAME to be fixed to backend name
instead of filename; while still making sure that
SANE_DEBUG_${BACKEND}* exist as documented in man pages.
Add references to epson and epson2 man pages about
SANE_DEBUG_EPSONx_SCSI and _NET options.
Created an epson2 man page; based mostly on epson page.
chris@cnpbagwell.com