if configure can't find `mkfifo', configure will look for `mknod',
and set MKFIFO to `mkfifo_using_mknod', which is a new script
that basically just invokes `mknod $1 p'. Also, add a new
option --no-demangle; if this option is used, or if the system doesn't
have either `mknod' or `mkfifo', then demangling is disabled.
These changes are all because some systems (e.g. SunOS 4.1.3)
don't have `mkfifo'.