swift234

Permit attribute lists to be split into multiple clauses.

This is particularly convenient for dealing with generated
code (e.g. as produced by the SIL printer), but it's also
quite defensible as a way for users to logically group
related attributes and split unrelated ones out, should
users find themselves using a lot of verbose attributes
(and prior experience with e.g. user-defined attributes
is that they definitely do sometimes turn into walls of
text...).

Swift SVN r7376