Make the Error class constructor protected

This is forcing to use Error::success(), which is in a wide majority
of cases a lot more readable.

Differential Revision: https://reviews.llvm.org/D26481

llvm-svn: 286561

llvm/lib/Object/MachOObjectFile.cpp

@@ -1073,7 +1073,7 @@ Expected<std::unique_ptr<MachOObjectFile>>
 MachOObjectFile::create(MemoryBufferRef Object, bool IsLittleEndian,
                         bool Is64Bits, uint32_t UniversalCputype,
                         uint32_t UniversalIndex) {
-  Error Err;
+  Error Err = Error::success();
   std::unique_ptr<MachOObjectFile> Obj(
       new MachOObjectFile(std::move(Object), IsLittleEndian,
                           Is64Bits, Err, UniversalCputype,