Makes the lint a bit more accurate, and improves the quality of the diagnostic
messages by explicitly returning an error message.
The new lint is also a little more aggressive: specifically, it now
rejects tuples, and it recurses into function pointers.
This commit moves the IR files in the distribution, rust_try.ll,
rust_try_msvc_64.ll, and rust_try_msvc_32.ll into the compiler from the main
distribution. There's a few reasons for this change:
* LLVM changes its IR syntax from time to time, so it's very difficult to
have these files build across many LLVM versions simultaneously. We'll likely
want to retain this ability for quite some time into the future.
* The implementation of these files is closely tied to the compiler and runtime
itself, so it makes sense to fold it into a location which can do more
platform-specific checks for various implementation details (such as MSVC 32
vs 64-bit).
* This removes LLVM as a build-time dependency of the standard library. This may
end up becoming very useful if we move towards building the standard library
with Cargo.
In the immediate future, however, this commit should restore compatibility with
LLVM 3.5 and 3.6.
At this time unwinding support is not implemented for MSVC as
`libgcc_s_seh-1.dll` is not available by default (and this is used on MinGW),
but this should be investigated soon. For now this change is just aimed at
getting the compiler far enough to bootstrap everything instead of successfully
running tests.
This commit refactors the `std::rt::unwind` module a bit to prepare for SEH
support eventually by moving all GCC-specific functionality to its own submodule
and defining the interface needed.
