This allows expressions such as ".foo" and ".foo(1)" to refer to
static variables and static methods, respectively, as well as enum
cases.
To get here, rework the parsing of delayed identifier expressions a
bit, so that the argument itself is part of the delayed argument
expression rather than a separate call expression. This simplifies
both the handling of patterns of this form and the type checker, which
can now user simpler constraints.
If we really want to support (.foo)(1), we can make that work, but it
seems unnecessary and perhaps confusing.
Swift SVN r10626
