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_sekizoa.cpp

@@ -255,7 +255,7 @@ int daObj_Sekizoa_c::CreateHeap() {
     }
     if (mType == TYPE_6) {
         int success_create = mInvModel.create(mpMorf[0]->getModel(), 1);
-        if (success_create == NULL) {
+        if (success_create == 0) {
             return 0;
         }
 
@@ -736,7 +736,7 @@ void daObj_Sekizoa_c::setAttnPos() {
         mpMorf[1]->modelCalc();
     }
     if (mpMcaMorf != NULL) {
-        ((mDoExt_McaMorfSO*)mpMcaMorf)->play(NULL, 0);
+        ((mDoExt_McaMorfSO*)mpMcaMorf)->play(0, 0);
         if (mType == TYPE_1 || mType == TYPE_3 || mType == TYPE_5) {
             mDoMtx_stack_c::copy(mpMorf[0]->getModel()->getAnmMtx(7));
         } else {