swift234

[AST] Use the short-form @available() syntax in the AST printer where possible.

Change the AST printer to use the new short-form @available attribute syntax for
attributes with only introduction versions. So, for example, a declaration
annotated as:

@available(iOS, introduced=8.0)
@available(OSX, introduced=10.10)
func foo()

will be printed as:

@available(iOS 8.0, OSX 10.10, *)
func foo()

We won't include the attribute on the short form if it has a deprecated or
obsoleted version; nor if it has a message, a rename, or marks unconditional
unavailability.

There is a corresponding change to the SourceKit tests.

rdar://problem/20982322

Swift SVN r28734