Add debug information analysis (#3305)

We need an analysis for OpenCL.DebugInfo.100 extension instructions such
as a map between function id and its DebugFunction. This commit add an
analysis for it.
diff --git a/BUILD.gn b/BUILD.gn
index d3107fd..5860aff 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -542,6 +542,8 @@
     "source/opt/decompose_initialized_variables_pass.h",
     "source/opt/decoration_manager.cpp",
     "source/opt/decoration_manager.h",
+    "source/opt/debug_info_manager.cpp",
+    "source/opt/debug_info_manager.h",
     "source/opt/def_use_manager.cpp",
     "source/opt/def_use_manager.h",
     "source/opt/desc_sroa.cpp",