$ escape sequences in quasis

[Mike Samuel]

2011/5/26 Waldemar <waldemar at google.com>:
> If unicode character u+1234 is an identifier character, then this is a
> substitution of a variable whose name is that one-letter identifier just
> like any other $foo substitution would be. If not, then this is the two
> characters $ and u+1234.

Good point about escape sequences that decode to characters in
IdentifierStart and IdentifierPart.  Will update the wiki grammar to
reflect that.