Test that ANSI input is filtered

Add a simple regression test to make sure ANSI escape sequences
aren't allowed in input lines. The escape (byte \x1b) character
should be filtered from non-binary-mode clients because we filter to
a "printable" set. For binary-mode clients an escape won't be valid
UTF-8 and so will cause the entire line of input on which it's found
to be skipped.