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_maro.cpp

@@ -386,7 +386,7 @@ int daNpc_Maro_c::Execute() {
         setSellItemMax(getMaxNumItem());
         field_0xf60 = -1;
         setMasterType(2);
-        mShopCamAction.setCamDataIdx(NULL);
+        mShopCamAction.setCamDataIdx(0);
         mShopCamAction.setCamAction(NULL);
         field_0x1131 = 1;
     }