Purpose: Fixed HDFFV-8922
Description:
    Added notes regarding UTF-8 and extended ASCII, provided in HDFFV-8899,
    to C++ API.
Platforms tested:
    Linux/32 2.6 (jam) - only in comments


git-svn-id: https://svn.hdfgroup.uiuc.edu/hdf5/trunk@25658 dab4d1a6-ed17-0410-a064-d1ae371a2980