Characters supported by TeX but not in Latin 1

[jxbardant]

Hello to all

I'm trying to typeset a Turkish song but I have some trouble with lyrics.
Turkish uses the following letters which are absent from Latin 1:
- s cedilla (TeX \cs)
- dotless i (\i)
- g with half circle (\ug)
- capital I with dot (\.I)

It seems I can't use TeX-like sequences like \ss, etc...
I didn't succeed either in using \char.

If I replace those characters with their ASCII equivalent (dotless i with i for 
instance) and edit later the generated TeX file to put back the Turkish 
characters I can get the result I want. This shows that the characters I want 
to use do exist in the lyrics and title fonts. But this method is really 
difficult to use since the lyrics are broken down in syllables and scattered 
everywhere in the file, plus if I change anything in the sore I have to do it 
again.

Is there another way to use those characters in Lilypond ?

TIA

JX Bardant