Fixed bug 2813 by making sure the default value is set for non-assigned variables.

Also added a compile error if a proc is defined with multiple of the same name variable, and fixed the target for compile errors with procs.
Allow braces in procs. This is somewhat a stopgap measure, but should be fully supportable in the future.
Merge branch 'master' of github.com:sk89q/commandhelper
Fix for bug 2811. Don't execute the sconcat at the root of a proc.

Since it's probably added automatically, and regardless, it won't be used, it's a waste of time to evaluate it.
Merge pull request #172 from EntityReborn/master

Some backend extension work to facilitate good things to come.
Don't catch such a broad exception.
Use a less sophisticated, but hopefully faster method for sudo.
Merge origin/master
Merge origin/master conflict fixes.