C++11 makes numerous additions to the list of Unicode code points
allowed in identifiers (   E). This includes the byte order mark, which
is included in range FE47-FFFD. However, this character is also used
as a prefix or envelope for UTF-16 and UTF-8 files.

The most reasonable thing for an implementation to do is ignore a BOM
at the beginning of a source file, but it's still possible (if
unlikely) to begin a file with an identifier.

Although this ambiguity is unlikely to occur, it probably makes more
sense to exclude the BOM from identifiers. It has been superseded by
WORD JOINER, U+2060, as the invisible, non-breaking space character
preferred for use in text. The latter is also allowed in identifiers,
for better or worse.

See also the discussion on Stack Overflow,
http://stackoverflow.com/questions/8227642/is-the-byte-order-marker-really-a-valid-identifier

     - D


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