Default reporter: line jump may be missed if failure message exceeds maximum message length

[cschreib]

With the default reporter only. If a test failure generates a message of length exceeding SNITCH_MAX_MESSAGE_LENGTH, the message is truncated. This is the expected behavior, except that currently the truncation can remove the end-of-line character, which then corrupts the terminal output. It can also remove reset-color markers, which means that coloring can leak to the next message.