Fix -Wmemset-transposed-args warnings of clang++

Fixes:
xercesc/util/XMLChTranscoder.cpp:73:23: warning: setting buffer to a 'sizeof' expression; did you mean to transpose the last two arguments? [-Wmemset-transposed-args]
    memset(charSizes, sizeof(XMLCh), countToDo);
                      ^
xercesc/util/XMLChTranscoder.cpp:73:23: note: cast the second argument to 'int' to silence

and

xercesc/util/XMLUTF16Transcoder.cpp:114:23: warning: setting buffer to a 'sizeof' expression; did you mean to transpose the last two arguments? [-Wmemset-transposed-args]
    memset(charSizes, sizeof(UTF16Ch), countToDo);
                      ^
xercesc/util/XMLUTF16Transcoder.cpp:114:23: note: cast the second argument to 'int' to silence
1 warning generated.
2 files changed