Changed SCP reading to scan all TDH entries
Changed SCP reading to scan all TDH entries

The start/end tracks don't seem well defined, so we now scan all entries
in the index and extract any found. The index structure is the same for
both single and double-sided images. Allow for 168 entries, but default
to scanning the original 166.

simonowen/samdisk,simonowen/samdisk,simonowen/samdisk