By default, g++ assumes -fmessage-length=72. I think this is not a good
idea because:

1. It breaks existing tools. E.g. emacs awaits a "<location>:<line>
<error-msg>" format and gets confused by the current behavior

2. It makes error-messages completely unreadable. E.g. if there are
messages saying something about templates, it's not unusual that the
template-parameter-list is splitted over several lines.

3. The value of 72 is IMHO obsoleted. Are there still existing C++
programmers  which are writing code on an 80-column console? I think most
ones are using xterms or framebuffer-screens with 100 or more columns.

4. Only the g++ frontend defaults to this linebreak. This is
inconsequentlally.