allow to use a lua without debug library

http/bit.lua

@@ -11,7 +11,7 @@ This means we can ignore the differences between bit libraries.
 if _VERSION ~= "Lua 5.1" then
     -- Lua 5.3+ has built-in bit operators, wrap them in a function.
 	-- Use debug.getinfo to get correct file+line numbers for loaded snippet
-	local info = debug.getinfo(1, "Sl")
+	local info = debug and debug.getinfo(1, "Sl") or { currentline = -1 }
 	local has_bitwise, bitwise = pcall(load(("\n"):rep(info.currentline+1)..[[return {
 		band = function(a, b) return a & b end;
 		bor = function(a, b) return a | b end;

http/h2_error.lua

@@ -49,7 +49,7 @@ function http_error_methods:new_traceback(message, stream_error, lvl)
 		message = message;
 		stream_error = stream_error;
 	}
-	if lvl ~= 0 then
+	if lvl ~= 0 and debug then
 		-- COMPAT: should be passing `nil` message (not the empty string)
 		-- see https://github.com/keplerproject/lua-compat-5.3/issues/16
 		e.traceback = debug.traceback("", lvl)