QSymbianTextCodec::init() on Symbian^4 (and ^3?) is too slow

Measurements that were mailed to me from somebody at Nokia showed that QSymbianTextCodec::init() takes up to 300ms on newer Symbian versions. I believe it is Symbian^4, but it could also be Symbian^3.
The apparent reason is that the static codec alias lookup table in qtextcodec_symbian.cpp has much less entries than the newer Symbian versions have codecs. Therefore, QSymbianTextCodec::init() will call the expensive ConvertCharacterSetIdentifierToStandardNameL (via IPC?) for each system codec taht is not in the aforementioned list.

Todo as fix: Verify if entries have to be added to that list, and then do it.