[PATCH] MC: Add support for BigObj

[Rui Ueyama]

LGTM

Because BigObj is only for object files and not for executables, we are not
going to use the writer for the linker, though.

================
Comment at: lib/MC/WinCOFFObjectWriter.cpp:884
@@ +883,3 @@
+        memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length);
+        Length = 0;
+      }
----------------
You can just break here.

================
Comment at: lib/MC/WinCOFFObjectWriter.cpp:887
@@ +886,3 @@
+
+      Offset = Offset + SymbolSize;
+    }
----------------
Offset += SymbolSize?

http://reviews.llvm.org/D5349