Fix #249: Guard against events not existing in MySQL 5.0
Merge pull request #250 from iarna/mysql-five-dot-oh

Fix #249: Guard against events not existing in MySQL 5.0
Fix guard against events not existing
Remove needless body rewriting

In earlier, more naive versions of the parser, ensuring that the bodies of
procs, events and triggers were always in BEGIN / END blocks was helpful,
but this has been unnecessary for a long time, and only adds needless room
for new errors to creep in.
Merge pull request #251 from iarna/remove-needless-body-rewriting

Remove needless body rewriting
Add schema validation as a feature
Whenever possible, produce error messages rather than exceptions