werrstr() takes a format string as its first argument.
a common error is to pass user controlled string buffers
into werrstr() that might contain format string escapes
causing werrstr() to take bogus arguments from the stack
and crash.
so instead of doing:
werrstr(buf);
we want todo:
werrstr("%s", buf);
or if we have a local ERRMAX sized buffer that we can override:
errstr(buf, sizeof buf);
