Pass "ignore" on decoding Google Code issue text to avoid bad characters
(such as in https://code.google.com/p/drmemory/issues/detail?id=1289#c3)
throwing an exception and aborting the migration.
Increase the max comment size before splitting into two GitHub comments
from 7000 to 9000.

I put this in because when we first noticed the comment reordering we
thought it was only on split comments.  With the 5s delay we don't need
this anymore, but note that the higher value seems to work.
Escape Markdown characters and convert cross-issue links.

GitHub interprets several different characters as Markdown, and our
GoogleCode issue text is full of these chars.  This change transforms the
body (first comment) and later comments by escaping these Markdown chars.

Converts cross-issue links from GoogleCode format to GitHub format.
Add 5 second delay between each comment to reduce reorderings.
Without this delay, a full 1 in 3 comments migrated from GoogleCode to
GitHub is out of order with respect to other comments on the same issue!

A better and faster solution might be to query after each posted comment
but that would also eat into the rate limit.  This simple solution worked
well though.
Change default logging to INFO to give a much better idea of the progress
of the migration.
Add custom label mappings for dynamorio and drmemory GoogleCode issue
trackers.

Add removal of unwanted labels.

Rename the "imported" label to "Migrated".
Rename local vars: s/imported/migrated/