swift234

Emit unique metadata for functions with inout

References to functions that take inout parameters crash the compiler
because InOutType isn't a "real" type in itself and has no special type
metadata to emit. It merely further qualifies the function's input
types.

For example, we would like to have a unique entry in the cache for:

var f: (T, T) -> ()

and

var f2: (inout T, T) -> ()

For each argument type metadata pointer in the function's input, take
advantage of pointer alignment and mark the lowest bit if it is inout.
Since the metadata cache uses pointers to create the key, this creates a
unique entry while still being able to extract the actual pointer.

This fixes <rdar://problem/17655125>, and a couple of other similar
crashes.

Swift SVN r23557