Adds:
- model/LocalVariableScopeInfo.h
Stores, for local variable blocks:
- the names of the local variables in the block
- the "base index" of those local variables within the current scope
The code generator uses these to clean up local variables as they go out of scope.
We also need this when writing debug information.
Adds:
- ast/UserFunction AST node for user-defined functions.
- astbuilder/AvailableUserFunction: reference to a parse tree for a user function.
- The AST builder only generates ASTs for user functions that are actually referenced.
- astbuilder/UserFunctionVisitor: visits (builds an AST for) a parse tree for a user function.
- This happens after the .src or .inc file has been otherwise processed, so this class serves to hook up the correct SourceFileIdentifier to the AST.
