[LLVM][DebugInfo] Add accessor for NameIndex header.

This is needed for pending LLD work to create a single unified .debug_names
index (rather than just appending all the indices from each .o file).

Author: cmtice

llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h

@@ -605,6 +605,9 @@ class DWARFDebugNames : public DWARFAcceleratorTable {
     NameIndex(const DWARFDebugNames &Section, uint64_t Base)
         : Section(Section), Base(Base) {}
 
+    /// Returns Hdr field
+    Header getHeader() const { return Hdr; }
+
     /// Reads offset of compilation unit CU. CU is 0-based.
     uint64_t getCUOffset(uint32_t CU) const;
     uint32_t getCUCount() const { return Hdr.CompUnitCount; }