[WinCOFF] Add support for the .safeseh directive

.safeseh adds an entry to the .sxdata section to register all the
appropriate functions which may handle an exception.  This entry is not
a relocation to the symbol but instead the symbol table index of the
function.

llvm-svn: 238641
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index 280dbe2..426bf90 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -555,6 +555,9 @@
   CurrentWinFrameInfo->PrologEnd = Label;
 }
 
+void MCStreamer::EmitCOFFSafeSEH(MCSymbol const *Symbol) {
+}
+
 void MCStreamer::EmitCOFFSectionIndex(MCSymbol const *Symbol) {
 }