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_lv3Water.cpp

@@ -31,7 +31,7 @@ public:
 };
 
 daLv3Water_HIO_c::daLv3Water_HIO_c() {
-    mLevelControlWaitFrames = NULL;
+    mLevelControlWaitFrames = 0;
 }
 
 #if DEBUG