safer curly braces checking
minor #538 safer curly braces checking (keradus)

This PR was squashed before being merged into the 1.0.x-dev branch (closes #538).

Discussion
----------

safer curly braces checking

- Safer check if token is { or }
- little speed impr. in `Tokens::getNamespaceUseIndexes`

Commits
-------

062b933 safer curly braces checking