[RogueC] Added unused class 'CmdGrouping'
[RogueC] Added unused class 'CmdGrouping'

- Was going to be part of overloading expression grouping with "operator()".
- Every paren'd expression would be wrapped in a CmdGrouping node.
- Realized that RogueC relies too heavily on parsing an expression then checking to see its type.
- Too risky to add CmdGrouping now.
- Left in code base for possible later use.

Plasmaworks/Rogue,AbePralle/Rogue,Plasmaworks/Rogue,Plasmaworks/Rogue,Plasmaworks/Rogue,AbePralle/Rogue