Greek characters on sms/phonebook input/output

The three letters '', '' and '' conflict in ISO-8859.

This should be displayed in greek terminal encoding:
greek	masked	character
	\D	capital delta
	\F	capital phi
	\C	capital psi

This should be displayed in latin terminal encoding:
latin	masked	character
	\A	A with diaeresis
	\O	O with diaeresis
	\/	O with stroke

You can switch between those two completely at compile time
(see config.h) and additionally at runtime:
--greek		use the above greek table
--nogreek	use the above latin table
Only one of those two options is available at runtime (see
output of --help). The masked sequences are independent of
this and can always be used. The above settings does not only
control the input but also the output! To be sure that download
and upload are really equal, the same setting has to be used!

For the other greek charactern, there are also masked inputs,
this should be displayed in greek terminal encoding:
greek	masked	character
	\G	capital gamma
	\L	capital lambda
	\V	capital omega
	\P	capital pi
	\S	capital sigma
	\U	capital theta
	\J	capital xi

The latin equivalents should match the greek ones on the greek keyboard layout.
