MC: Implement support for new .addrsig and .addrsig_sym directives.

Part of the address-significance tables proposal:
http://lists.llvm.org/pipermail/llvm-dev/2018-May/123514.html

Differential Revision: https://reviews.llvm.org/D47744

llvm-svn: 337328
diff --git a/llvm/lib/ObjectYAML/ELFYAML.cpp b/llvm/lib/ObjectYAML/ELFYAML.cpp
index 8964f5c..f916b5d 100644
--- a/llvm/lib/ObjectYAML/ELFYAML.cpp
+++ b/llvm/lib/ObjectYAML/ELFYAML.cpp
@@ -444,6 +444,7 @@
   ECase(SHT_LLVM_ODRTAB);
   ECase(SHT_LLVM_LINKER_OPTIONS);
   ECase(SHT_LLVM_CALL_GRAPH_PROFILE);
+  ECase(SHT_LLVM_ADDRSIG);
   ECase(SHT_GNU_ATTRIBUTES);
   ECase(SHT_GNU_HASH);
   ECase(SHT_GNU_verdef);