Add upgrade statements for those upgrading from previous versions of volunteer

Could you add this to the mysql statement. I have seen mysql statements that check if the table exists it creates it, otherwise it upgrades. Otherwise put these statements in comments and say what version of volunteer it worked on.

Volunteer_contact_event
alter table volunteer_contact_event change eid nid int(10) unsigned NOT NULL default '0';
alter table volunteer_contact_event add primary key (nid, cid);

Volunteer
alter table volunteer change eid nid int(10) unsigned NOT NULL default '0';