Proposed resolution (July, 2009):
Change 5.13.3 [lex.ccon] paragraph 2 as follows:
...The value of a wide-character literal containing a single c-char has value equal to the numerical value of the encoding of the c-char in the execution wide-character set, unless the c-char has no representation in the execution wide-character set, in which case the value is implementation-defined. [Note: The type wchar_t is able to represent all members of the execution wide-character set, see 6.8.2 [basic.fundamental]. —end note]. The value of a wide-character literal containing multiple c-chars is implementation-defined.
Change 5.13.3 [lex.ccon] paragraph 5 as follows:
A universal-character-name is translated to the encoding, in the appropriate execution character set, of the character named...