What tools do you use to develop Oracle stored procedures, in a team :
Using Source Control for Oracle you get a lot of what you're looking for.
Stored procedures (as well as packages, functions, tables etc.) can be locked manually using the interface, not automatically, but this does prevent others making changes.
The new SQL to create the object can then be checked into SVN or TFS (no CVS support unfortunately).
The tool is not free but has a free 28-day trial.