Fix COFF section index relocation should be 16 bits, not 32

Original patch by Andrey Guskov!
http://reviews.llvm.org/D5651

llvm-svn: 219327
diff --git a/llvm/lib/MC/WinCOFFStreamer.cpp b/llvm/lib/MC/WinCOFFStreamer.cpp
index b8d5f2a..078091c 100644
--- a/llvm/lib/MC/WinCOFFStreamer.cpp
+++ b/llvm/lib/MC/WinCOFFStreamer.cpp
@@ -163,7 +163,7 @@
   const MCSymbolRefExpr *SRE = MCSymbolRefExpr::Create(Symbol, getContext());
   MCFixup Fixup = MCFixup::Create(DF->getContents().size(), SRE, FK_SecRel_2);
   DF->getFixups().push_back(Fixup);
-  DF->getContents().resize(DF->getContents().size() + 4, 0);
+  DF->getContents().resize(DF->getContents().size() + 2, 0);
 }
 
 void MCWinCOFFStreamer::EmitCOFFSecRel32(MCSymbol const *Symbol) {