swift234

Emit entrypoints for the default argument generator functions.

In the resilience model for default arguments, the presence of a
default argument is API, but its specific value is not. Thus, the
actual default argument values can evolve over time. To implement
this, for each default argument, we emit a function that
takes no arguments and produces the default value for that
argument. The caller will then call that function to form the default
argument.

This commit emits these functions for each default argument, even
though they are not currently being called. This is part of
<rdar://problem/11561185>.

We'll probably want a different calling convention for these functions
that preserves all registers, since they will often end up being very
trivial functions. 




Swift SVN r6260