More GCC compatibility/warning fixes (#3118)

* Wrap >4-char literals in a MULTI_CHAR macro

Modern compilers do not support CW's non-standard behavior with
>4 char literals. We can, however, use a constexpr function to
compute the u64 values directly. This leaves <=4 char literals
unchanged.

* Replace non-pointer usages of NULL with 0

* Define NULL to nullptr on C++11 and above

* Fix more -Wpointer-arith and -Woverflow warnings

* Replace u32/s32 with uintptr_t/intptr_t where appropriate

* JSUOutputStream: Overload all standard int types

src/d/d_s_name.cpp

@@ -339,7 +339,7 @@ scene_process_profile_definition g_profile_NAME_SCENE = {
     0,
     &g_fopScn_Method.base,
     &l_dScnName_Method,
-    NULL,
+    0,
 };
 
 scene_process_profile_definition g_profile_NAMEEX_SCENE = {
@@ -353,5 +353,5 @@ scene_process_profile_definition g_profile_NAMEEX_SCENE = {
     0,
     &g_fopScn_Method.base,
     &l_dScnName_Method,
-    NULL,
+    0,
 };