[llvm-dwarfdump] - Teach tool about few GNU call_sites constants.

This teaches tool about following consants: 
DW_TAG_GNU_call_site,
DW_TAG_GNU_call_site_parameter,
DW_AT_GNU_call_site_value,
DW_AT_GNU_all_call_sites.

Constants documented here: https://sourceware.org/elfutils/DwarfExtensions

Differential revision: https://reviews.llvm.org/D39119

llvm-svn: 316321
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
index 1b5744e..a534d36 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
@@ -234,7 +234,8 @@
   else if (Attr == DW_AT_decl_line || Attr == DW_AT_call_line)
     OS << *formValue.getAsUnsignedConstant();
   else if (Attr == DW_AT_location || Attr == DW_AT_frame_base ||
-           Attr == DW_AT_data_member_location)
+           Attr == DW_AT_data_member_location ||
+           Attr == DW_AT_GNU_call_site_value)
     dumpLocation(OS, formValue, U, sizeof(BaseIndent) + Indent + 4, DumpOpts);
   else
     formValue.dump(OS, DumpOpts);