Update hash table implementation to only use CityHash.

Instead of switching hash functions altogether, we just use different
seeds for CityHash. This isn't perfect since there is correlation
between the resulting hashes (https://131002.net/siphash/ contains more
details). The next hash table patch will update the bucket selection
algorithm to use a (2, 4) hashing scheme to try to improve space/cache
utilization, as well as improving lookup times.

git-svn-id: https://pennmush.googlecode.com/svn/trunk@1834 ba372814-4f39-11de-9ad6-1127a62b9fcd
Add an #include for services.c

Since this file is only built on Windows, it didn't get updated during
the last set of patches to try to trim down the dependencies between
header files.

git-svn-id: https://pennmush.googlecode.com/svn/trunk@1835 ba372814-4f39-11de-9ad6-1127a62b9fcd