substructing a diff in caretPos to support connected languages

Some languages, such as arabic or persian, have characters that automatically connect to each other.
example:
ىىىىىىىىىىىىىىىىىىىىىىىىى
while each letter separated is:
ى ى ى ى ى ى.
that makes the mirror div look like that, seperated in the middle where the caret position is:
ىىىىىىىىىىىىى ىىىىىىىىىىىى
and causing the 'caretPos' method return false results.

My changes are: adding another mirror div, "mirrorfull", this time a full one without the caret span in the middle,
subtracting the width of mirrorfull and mirror to result the difference caused because of the caret span.