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_fairy.cpp

@@ -883,7 +883,7 @@ void daNpc_Fairy_c::srchActors() {
 
 BOOL daNpc_Fairy_c::evtTalk() {
     if (chkAction(&daNpc_Fairy_c::talk)) {
-        (this->*mAction)(NULL);
+        (this->*mAction)(0);
     } else {
         mPreItemNo = 0;
 
@@ -952,7 +952,7 @@ void daNpc_Fairy_c::action() {
     }
 
     if (mAction) {
-        (this->*mAction)(NULL);
+        (this->*mAction)(0);
     }
 }
 
@@ -1124,7 +1124,7 @@ BOOL daNpc_Fairy_c::setAction(actionFunc action, int param_2) {
     mMode = 0xFFFF;
 
     if (mAction) {
-        (this->*mAction)(NULL);
+        (this->*mAction)(0);
     }
 
     mMode = 0;