Substantially reduced time required to verify program memory contents.

Now verification consists of dumping program (i.e. flash) memory
in a block from first address in given hex file to last non-config
address in given hex file and then comparing given values with read
values. As before, quits upon first mismatch found.

Relatedly, code to perform a program memory dump has been moved to
a dedicated function, dump_pm.

git-svn-id: https://svn.code.sf.net/p/goodfet/code/trunk@466 12e2690d-a6be-4b82-a7b7-67c4a43b65c8