Fixed pfi::data::string::detail::chars_to_uchars to check two restriction.
Fixed pfi::data::string::detail::chars_to_uchars to check two restriction.

* Check given byte sequence is less than or equal to U+10FFFF when it is 4-byte sequence.
* Check decoded code point is not surrogate(it is not in range of [0xD800, 0xDFFF])

And added details to exception messages when given string is invalid.

retrieva/pficommon,pfi/pficommon,retrieva/pficommon,pfi/pficommon,takei-yuya/pficommon,retrieva/pficommon,takei-yuya/pficommon,takei-yuya/pficommon,retrieva/pficommon,pfi/pficommon,pfi/pficommon,takei-yuya/pficommon,retrieva/pficommon