Basic validation of UTF-8 input via GET/POST vars: invalid UTF-8 sequences will cause...

Basic validation of UTF-8 input via GET/POST vars: invalid UTF-8 sequences will cause the string to drop. Not necessarily super-thorough; should be improved in future to drop individual bad sequences, do normalization of combining forms, etc. General input validation (for ints, types of strings, etc) still would be good to have!