Merge branch 'master' into v2.1

Author: Mike Pall

src/jit/bcsave.lua

@@ -133,7 +133,7 @@ local function bcsave_c(ctx, output, s)
   local fp = savefile(output, "w")
   if ctx.type == "c" then
     fp:write(format([[
-#ifdef _cplusplus
+#ifdef __cplusplus
 extern "C"
 #endif
 #ifdef _WIN32