tapboard processor: Make file errors more explicit

perror() any time there's an EOF or a read error.
grouper: Handle EOF case when EOF happens during NAND read

Before, we'd crash out.  Now we handle this case correctly.
window: Add "pattern skip" for xor overlay

The "xor pattern" feature is useful, but sometimes there are off-by-one
errors.  The ability to start the xor pattern at a nonzero offset can
help overcome these problems.
Merge branch 'master' of git://github.com/bunnie/nandsee

A bit of an ugly merge.

Conflicts:
	nandseewindow.ui
histogramview: Move histogram stuff to its own view
Merge branch 'master' of git://github.com/bunnie/nandsee

Conflicts:
	nandsee.pro
	nandseewindow.cpp
	nandseewindow.h
	nandseewindow.ui
nandseewindow: Fix changes to nandseewindow
fix automated xor optimization