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_b_dr.cpp

@@ -4083,7 +4083,7 @@ int daB_DR_c::create() {
                 gravity = -3.0f;
 
                 mSound.init(&current.pos, &eyePos, 3, 1);
-                mColliderStts.Init(0x19, NULL, this);
+                mColliderStts.Init(0x19, 0, this);
 
                 fopAcM_OnStatus(this, 0x4000);