Remove LLVM_NOEXCEPT and replace it with noexcept

Now that we have dropped MSVC 2013, all supported compilers support
noexcept and we can drop this portability macro.

llvm-svn: 284672

llvm/lib/Support/Error.cpp

@@ -28,7 +28,7 @@ namespace {
   // deal with the Error value directly, rather than converting to error_code.
   class ErrorErrorCategory : public std::error_category {
   public:
-    const char *name() const LLVM_NOEXCEPT override { return "Error"; }
+    const char *name() const noexcept override { return "Error"; }
 
     std::string message(int condition) const override {
       switch (static_cast<ErrorErrorCode>(condition)) {