Replace Program with TranslationUnit
Add VariableDefinitionData

Combine MutableVariableDefinitionData
and ImmutableVariableDefinitionData
into VariableDefinitionData.
Add CharacterLiteral and CharacterLiteralData
Add StringLiteral and StringLiteralData
Add CharacterLiteralExpressionData
Add StringLiteralExpressionData
Merge pull request #30 from kmc-jp/ast

ASTを微修正