trans: Upgrade LLVM

This brings some routine upgrades to the bundled LLVM that we're using, the most
notable of which is a bug fix to the way we handle range asserts when loading
the discriminant of an enum. This fix ended up being very similar to f9d4149c
where we basically can't have a range assert when loading a discriminant due to
filling drop, and appropriate flags were added to communicate this to
`trans::adt`.

src/librustc_llvm/lib.rs

@@ -56,7 +56,7 @@ pub use self::DiagnosticSeverity::*;
 pub use self::Linkage::*;
 pub use self::DLLStorageClassTypes::*;
 
-use std::ffi::CString;
+use std::ffi::{CString, CStr};
 use std::cell::RefCell;
 use std::slice;
 use libc::{c_uint, c_ushort, uint64_t, c_int, size_t, c_char};
@@ -2404,6 +2404,20 @@ pub fn initialize_available_targets() {
     init_pnacl();
 }
 
+pub fn last_error() -> Option<String> {
+    unsafe {
+        let cstr = LLVMRustGetLastError();
+        if cstr.is_null() {
+            None
+        } else {
+            let err = CStr::from_ptr(cstr).to_bytes();
+            let err = String::from_utf8_lossy(err).to_string();
+            libc::free(cstr as *mut _);
+            Some(err)
+        }
+    }
+}
+
 // The module containing the native LLVM dependencies, generated by the build system
 // Note that this must come after the rustllvm extern declaration so that
 // parts of LLVM that rustllvm depends on aren't thrown away by the linker.