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_obj_so.cpp

@@ -831,7 +831,7 @@ static void demo_camera(obj_so_class* i_this) {
             // fallthrough
         case 2:
             sp3c.set(12459.0f, 3152.0f, 4628.0f);
-            daPy_getPlayerActorClass()->setPlayerPosAndAngle(&sp3c, 0xfffffaee, 0);
+            daPy_getPlayerActorClass()->setPlayerPosAndAngle(&sp3c, -1298, 0);
             i_this->mDemoCamCenter.x = a_this->current.pos.x;
             i_this->mDemoCamCenter.z = a_this->current.pos.z;
             sp3c.y = (a_this->current.pos.y + 150.0f) - 50.0f;