swift234

Accept limitations of LLVM build system

1) Move the low-level runtime code into swift/runtime
2) Move the high-level "standard library" code into swift/stdlib

The key difference is that the 'runtime' contains language support logic
(like retain/release logic) that the compiler assumes to always exist
and may assume intimate details about the implementation. This library
will have intimate knowledge of the swift ABI.

In contrast, the 'stdlib' can be completely rewritten and the
language/compiler make little if any assumptions about it. It is
expected to reexport fundamental types and operators, and implement
fundamental policies (precedence, implicit conversions, etc).

Swift SVN r3045