I still haven't added a :set function yet since I'm not sure if there's
a way to avoid the chain of boundp checks.

In this revision, I simplified the code a tiny bit wrt calculating the
translation table since I no longer use the indian-make-hash function
but call whatever functions it call directly in
tamil--update-quail-rules: this greatly reduces the amount of massaging
that needs to be done.

Also, can someone guide me to write a sort function for
quail-tamil-itrans-compute-syllable-table please?  The ideal order of
consonants should be the same as the one in the default value of
tamil-consonant-translation, same for tamil-vowel-translation.  I tried
the following

    (sort (reverse (mapcar #'car tamil-consonant-translation))
          (lambda (x y) (let ((lx (length x))
                              (ly (length y)))
                           (if (= lx ly) (string-lessp x y) (< lx ly)))))


but that definitely doesn't do what I want.  The idea was to sort the
list so that the basic consonants (க் ங் ச் etc.) first then the composite
ones (க்‌ஷ் க்ஷ் etc.) but `string-lessp' does not even sort the basic
consonants in the right order (the right order being the order in the
default value of `tamil-consonant-translation').

Can I use the min-width property in buffer text?  I'm not sure if it was
finished since I remember some discussion surrounding that it wasn't
quite finished yet.  I would like to try to use it for syllable table
and friends.