Doc: HTML table cells are misleadingly associated: should be top-aligned

[Mark D. Blackwell]

In section 2.2.1 of the Extending LilyPond manual (just for example):

http://www.lilypond.org/doc/v2.19/Documentation/extending/scheme-function-definitions

we see this table row:

typeN?      a Scheme type predicate...

However, the (Firefox) browser (for one) starts displaying the cell "a
Scheme type predicate..." at least five text lines higher than the
cell "typeN?".

The browser starts displaying "a Scheme type predicate..." much more
closely to "argN" (from the previous row). In fact, it's merely a
single line lower than "argN".

This mis-association of table cells makes reading the tables more
difficult. Plus, it seems unaesthetic.

The CSS stylesheet (for the HTML versions of all the documentation)
IMO should be changed so it top-aligns all table cells.