Make markup commands \super and \sub produce correct placement

Make markup commands \super and \sub produce correct placement

While the exact amount the super-/subscript is raised/lowered
is not standarized (different fonts and programs use slightly
different values), previous values used by LilyPond were
obviously absurd.  Look at the Wikipedia article
http://en.wikipedia.org/wiki/Subscript_and_superscript
to see some examples - they clearly show that the previous
value was wrong.

I've used values similar to LaTeX defaults.

[dak, 2013-10-16 15:29:24]

Well, one thing to note is that LilyPond should be more concerned about placing,
say, flats and sharps in a reasonable relation to a chord symbol (usually
uppercase) than to place mathematical super- and subscripts like expected.

Of course we should go for both if feasible, but I don't see that aspect
mentioned at all.

[lemzwerg, 2013-10-16 15:51:22]

LGTM