Moved lunit to third_party for Google compliance.

Makefile

@@ -445,7 +445,7 @@ testlua: lua
 	@set -e  # Abort on error.
 	@for test in $(LUATESTS) ; do \
 	  echo LUA $$test; \
-	  LUA_PATH="tests/bindings/lua/lunit/?.lua;upb/bindings/lua/?.lua" \
+	  LUA_PATH="third_party/lunit/?.lua;upb/bindings/lua/?.lua" \
 	    LUA_CPATH=upb/bindings/lua/?.so \
 	    lua $$test; \
 	done

third_party/lunit/README.google

@@ -0,0 +1,9 @@
+URL: https://github.com/dcurrie/lunit
+Version: 0.5
+License: MIT
+License File: LICENSE
+Description:
+A unit testing library for Lua.
+
+Local Modifications:
+Extracted the two file we actually need from the distribution.