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_batta.cpp

@@ -509,7 +509,7 @@ int daObjBATTA_c::execute() {
     action();
     mBrk->play();
     mBtk->play();
-    mpMorf->play(NULL, dComIfGp_getReverb(fopAcM_GetRoomNo(this)));
+    mpMorf->play(0, dComIfGp_getReverb(fopAcM_GetRoomNo(this)));
     mtx_set();
     if (field_0x9f0 == 0) {
         mSph.SetC(current.pos);