Improved(?) hash function.

Given the existing interface, it's quite tricky to use most popular hash
functions without a change, so I'm using a modified version of FNV1a.
The current function always starts with a seed of 0 (and will in user
functions), so I'm adding the offset each time instead. I'm not sure if
that will work as well.
Remove executable flag from jamfile.
Another try at an improved hash function.

This is based on the mix function from MurmurHash. It's not the full
algorithm as it's always seeded with 0, and doesn't do a final mix. This
should be okay as Boost.Hash doesn't claim to avalanche the bits.
Add metadata
Json meta data.
Add maintainers to metadata.
Typo
Update maintainers from /libs/maintainers.txt
Regenerate libraries.json
Regenerate metadata, alphabetical order + no empty maintainers.
Merge branch 'develop'

Library metadata, plus improved hash_combine.