Synchronize Vec3Pool to fix mod concurrency issues. Fixes #240.

Some mods access Vec3Pool in a thread-unsafe manner, causing
java.lang.NullPointerException at aok.a(Vec3Pool.java:123) crashes
on MCPC+, fairly frequently in some configurations. Synchronize the
Vec3Pool methods to fix this issue.

Thanks to nallar for this fix.
Update to Forge 7.7.1.614
Faster UUID for entities

It is overkill to create a new SecureRandom on each entity create and then use it to make a new Entity ID for every entity instance created. Instead we will just use a pseudo random UUID based off the random