This overload is a raw decoding function and decodes the data into the
provided buffer @a dst of the given size @e dstLen. An error is returned if
the buffer is not large enough -- that is not at least
- wxBase64DecodedSize(srcLen) bytes.
+ wxBase64DecodedSize(srcLen) bytes. Notice that the buffer will @e not be
+ @NULL-terminated.
This overload returns the number of bytes written to the buffer or the
necessary buffer size if @a dst was @NULL or @c wxCONV_FAILED on error,