Fix problems with non-ASCII characters in queries

[ianmcook]

Some functions in queryparser work fine with input that includes Unicode characters, but other functions cause warnings or throw errors. Add a comprehensive set of tests for input that contains Unicode characters, and make all the changes necessary to get these functions to pass.

[ianmcook]

Most problems with non-ASCII characters should now be fixed, but the current set of tests is non-comprehensive so it's possible that warnings or errors might still occur when there are non-ASCII characters in some types of queries.