[Support] Make ErrorAsOutParameter take an Error* rather than an Error&.

This allows ErrorAsOutParameter to work better with "optional" errors. For
example, consider a function where for certain input values it is known that
the function can't fail. This can now be written as:

Result foo(Arg X, Error *Err) {
  ErrorAsOutParameter EAO(Err);

  if (<Error Condition>) {
    if (Err)
      *Err = <report error>;
    else
      llvm_unreachable("Unexpected failure!");
  }
}

Rather than having to construct an ErrorAsOutParameter under every conditional
where Err is known to be non-null.

llvm-svn: 276430
diff --git a/llvm/lib/Object/MachOObjectFile.cpp b/llvm/lib/Object/MachOObjectFile.cpp
index 563236f..262dbe1 100644
--- a/llvm/lib/Object/MachOObjectFile.cpp
+++ b/llvm/lib/Object/MachOObjectFile.cpp
@@ -267,7 +267,7 @@
       DataInCodeLoadCmd(nullptr), LinkOptHintsLoadCmd(nullptr),
       DyldInfoLoadCmd(nullptr), UuidLoadCmd(nullptr),
       HasPageZeroSegment(false) {
-  ErrorAsOutParameter ErrAsOutParam(Err);
+  ErrorAsOutParameter ErrAsOutParam(&Err);
   uint64_t BigSize;
   if (is64Bit()) {
     parseHeader(this, Header64, Err);