[pr19844] Add thread local mode to aliases.

This matches gcc's behavior. It also seems natural given that aliases
contain other properties that govern how it is accessed (linkage,
visibility, dll storage).

Clang still has to be updated to expose this feature to C.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209759 91177308-0d34-0410-b5e6-96231b3b80d8
Fix standard integer definitions for MSVC in DataTypes.h

Previously, DataTypes.h would #define a variety of symbols any time
they weren't already defined.  However, some versions of Visual
Studio do provide the appropriate headers, so if those headers are
included after DataTypes.h, it can lead to macro redefinition
warnings.

The fix is to include the appropriate headers if they exist, and
only #define the symbols if the required header does not exist.

Patch by Zachary Turner!

---

The big change here is that we no longer have our own stdint.h
typedefs because now all supported toolchains have stdint.h.
Hooray!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209760 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "InstCombine: Improvement to check if signed addition overflows."

This reverts commit r209746.

It looks it is causing a crash while building libcxx. I am trying to get a
reduced testcase.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209762 91177308-0d34-0410-b5e6-96231b3b80d8