Give es_ES.UTF-8 the highest weight in languages.xml

This is kind of arbitrary, Spain isn’t the country with the biggest
number of Spanish speaking people, but that is what Anaconda’s
mangleMap did so far and it is not clear which territory to put first
in that list anyway.
Fix typo in locale for Sinhala (should be si_LK.UTF-8)
Add test cases to make sure mamangleLocale(inLocale) is reproduce good enough