swift234

[func-sig-opts] Enable function sig opts on fragile functions.

Previously, we used shared linkage and did not specialize fragile functions
since this exposed serialization issues. These serialization issues have been
dealt with but I realized the model did not make sense: We do not specialize
functions with "external" linkage. This means that we only specialize functions
in the module in which it is defined. Thus shared provides no benefit in terms
of the linker being able to squash the function. Instead we just copy whatever
linkage the original function used.

rdar://16917049

Swift SVN r22940