pp.c: Remove disabled code for context sensitive lc

pp.c: Remove disabled code for context sensitive lc

This code was always #ifdef'd out.  It would have been used to convert
to a Greek final sigma from a non-final one, depending on context.  The
problem is that we can't know algorithmically if a final sigma is in
order or not.  I excerpt this quote, that I find persuasive, from
correspondence from Father Chrysostomos, who knows Greek:

"I cannot see how any algorithm can know to get it right.

"The letter σ (or Σ in capitals) represents the number 200 in Greek
numerals.  Those are not just ancient Greek numerals, but are used on a
regular basis even in modern Greek.  In many printed books ς is used in
place of ϛ, which represents the number 6.  So if casefolding should
change ͵ΑΣʹ to ͵αςʹ, or if an output layer changes ͵ασʹ similarly, it
will be changing the number (from 1200 to 1006).  You can’t get around
it by checking for the Greek numeral sign (ʹ), as sometimes the tonos
(΄), oxeia (´), or even the ASCII straight quote is used.  And often in
lists or chapter titles a dot is used instead of numeral sign.

"Also, σ is commonly used at the ends  of abbreviations. Changing ‘βλέπε
σ. 16’ (‘see page 16’) to ‘βλέπε ς. 16’ is not acceptable.

"So, no, I don’t think a programming language should be fiddling with σ
versus ς.  (A word processor is another matter.)"