[StackMaps] Add a lightweight parser for stackmap version 1 sections.

The parser provides a convenient interface for reading llvm stackmap v1 sections
in object files.

This patch also includes a new option for llvm-readobj, '-stackmap', which uses
the parser to pretty-print stackmap sections for debugging/testing purposes.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240860 91177308-0d34-0410-b5e6-96231b3b80d8

tools/llvm-readobj/ObjDumper.h

@@ -52,6 +52,8 @@ public:
   virtual void printCOFFDirectives() { }
   virtual void printCOFFBaseReloc() { }
 
+  virtual void printStackMap() const = 0;
+
 protected:
   StreamWriter& W;
 };