More TODO reorganization.

Hopefully we can get through all of the short term list by the next FF17-ESR
point release.
Remove Gitian result files from bundles. Include hashes instead.

The Gitian result files contain information about the full set of packages on
the system, which changes too often and doesn't normally otherwise alter build
output.
Fix permissions differences in omni.ja files.
Set a umask during input fetch, so langpacks and mingw inputs match.
Attempt to use MinGW hardening for Windows

Too bad it causes everything to insta-crash :/.
Update the TODO file.