[llvm-pdbutil] Add the ability to explain binary files.

Using this, you can use llvm-pdbutil to export the contents of a
stream to a binary file, then run explain on the binary file so
that it treats the offset as an offset into the stream instead
of an offset into a file.  This makes it easy to compare the
contents of the same stream from two different files.

llvm-svn: 329207
diff --git a/llvm/tools/llvm-pdbutil/llvm-pdbutil.h b/llvm/tools/llvm-pdbutil/llvm-pdbutil.h
index 82f4e52..811faf6 100644
--- a/llvm/tools/llvm-pdbutil/llvm-pdbutil.h
+++ b/llvm/tools/llvm-pdbutil/llvm-pdbutil.h
@@ -190,8 +190,11 @@
 } // namespace pdb2yaml
 
 namespace explain {
+enum class InputFileType { PDBFile, PDBStream, DBIStream, Names, ModuleStream };
+
 extern llvm::cl::list<std::string> InputFilename;
 extern llvm::cl::list<uint64_t> Offsets;
+extern llvm::cl::opt<InputFileType> InputType;
 } // namespace explain
 
 namespace exportstream {