Implemented some fixes to the code for compatibility with Python 2.6.

Some slots were not merged and some had wrong crate number.
To fix this I had to do basically a complete rewrite of the script.
However, now it looks much nicer :)

This script merges map files based on input list into a single map file.
It currently ingores the comment lines.
It also ignores next keywords: MASK, NSUBADD, BSUB. They are not currently
used.