Fix positions of statements

[tyamagu2]

• Fix Idx1 of BranchStatement so that it points to the character after the label if Label exists, or the one after Token if Label does not exist.
• Fix Idx1 of LabelledStatement so that it points to the character after the statement.
• Fix Idx1 of ReturnStatement so that it points to the character after the argument if Argument exists, or the one after return keyword if Argument does not exist.
• Set Idx0 of SwitchStatement and fix Idx1 of SwitchStatement so that it points to the character after the right brace.
• Fix Idx0 of ThrowStatement to point to the start of throw keyword and fix Idx1 of ThrowStatement so that it points to the next character after Argument.
• Fix Idx1 of TryStatement to point to the character after Finally if Finally exists, or after Catch if Finally does not exist.
• Set Idx0 of WithStatement which was not previously set.
• Set WhileStatement.While so that Idx0 points to the right place.
• Set Idx0 of DoWhileStatement and fix Idx1 to point to the next character after the right parenthesis.