added special case with an empty ICU chain for 'raw' index processing without call...

added special case with an empty ICU chain for 'raw' index processing without call of transliterators, case maps or tokenizators. It's optimized such that the following happens:
if (!chain->sort), no utf8 to utf16 translation occurs, and the original cstring is returned for the icu_chain-get_norm8() call.
if (chain->sort), utf8 to utf16 translation is made, the original cstring is returned for the icu_chain-get_norm8() call, and the utf16->sortkey conversion is run previous of calling icu_chain-get_sort8().