Consider moving text truncation tests to a separate test suite

[qerub]

…since it's rather implementation-specific and a little stop gap in porting.

(For reference: I discussed this with @client9 in a chat.)

[client9]

e.g. AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAB was in tests/test-tokens-words-001.txt tests/test-tokens-string-002.txt