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/actor/d_a_npc_hanjo.cpp

@@ -1791,7 +1791,7 @@ int daNpc_Hanjo_c::takayose(void* param_0) {
                 }
             }
         }
-        if (daPy_py_c::checkNowWolf() && mCyl2.ChkCoHit() != NULL) {
+        if (daPy_py_c::checkNowWolf() && mCyl2.ChkCoHit() != 0) {
             if (!daPy_getPlayerActorClass()->checkPlayerFly() ||
                 daPy_getPlayerActorClass()->checkAutoJump() ||
                 daPy_getPlayerActorClass()->checkWolfTriggerJump())