MachO: support N_INDR aliases in assembly files.

This makes LLVM create N_INDR aliases (to be resolved by the linker) when
appropriate.

rdar://problem/15125513

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209894 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Object/SymbolicFile.h

@@ -86,6 +86,7 @@ public:
     SF_Weak = 1U << 2,           // Weak symbol
     SF_Absolute = 1U << 3,       // Absolute symbol
     SF_Common = 1U << 4,         // Symbol has common linkage
+    SF_Indirect = 1U << 5,
     SF_FormatSpecific = 1U << 5  // Specific to the object file format
                                  // (e.g. section symbols)
   };