String.Buffer problem with mixed-width strings

Imported from http://bugzilla.roxen.com/bugzilla/show_bug.cgi?id=1679

Reported by Jonas Wallden jonasw@roxen.com

lister:jonasw $ ./pike-sås/7.2/bin/pike
Pike v7.2 release 37 running Hilfe v2.0 (Incremental Pike Frontend)
> object b = String.Buffer();
Result: Buffer(0 /* 0 */)
> b->add("a");
Result: 21
> b->add("\1234");
Result: 24
> b->add("b");
Result: 26
> b->add("\2345");
Result: 28
> b->add("c");
Result: 30
> b->get();
Result: "\1234ab\2345c"

The first addition of a wide string is incorrectly put at the beginning of the buffer. Later additions appear to work better.