define-composed-chars had the following combination defined:

'E' + '?' = 'Ë'

The '?' is used to add tildes, though. So it should be:

'E' + ':' = 'Ë'

'Ẽ' and 'ẽ' (capital 'E' and small 'e' with tildes) are \u1ebc and \u1ebd, 
respectively. This patch moves 'Ë' to the right set of characters 
(diaeresis/umlaut) and adds 'Ẽ' and 'ẽ' to the tilde set.

'Ẽ' and 'ẽ' don't show properly in my terminal font, so, sorry if I've 
mixed anything -- the three characters in question are:

\u00cb  00cb    LATIN CAPITAL LETTER E WITH DIAERESIS
Ẽ       1ebc    LATIN CAPITAL LETTER E WITH TILDE
ẽ       1ebd    LATIN SMALL LETTER E WITH TILDE


Patch is against current CVS. I assume that's what's desired. Same with my 
having attached it (rather than inline). Please chide me if either 
assumption is wrong. I expect I'll be submitting more patches. (not just 
for this issue)

Best,
Ben