mule-tests input method tests failing

[Stephen J. Turnbull]

Aidan Kehoe writes:

 > Update your leim package to at least 1.25, which includes the latin-4-prefix
 > and latin-5-prefix input methods.

Not acceptable.  Core tests should not fail because of the absence or
age of packages.  Fix the tests to be skipped, not failed, if the
input methods are missing, please.  Skip-Test-Unless will make loud
enough noises to warn the user; it doesn't need to fail, too.