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_bed.cpp

@@ -30,7 +30,7 @@ void daObj_Bed_HIO_c::genMessage(JORMContext* ctx) {
 }
 #endif
 
-daObj_Bed_HIOParam const daObj_Bed_Param_c::m = {NULL, -3.0f, 1.0f, 600.0f};
+daObj_Bed_HIOParam const daObj_Bed_Param_c::m = {0, -3.0f, 1.0f, 600.0f};
 
 daObj_Bed_c::~daObj_Bed_c() {
     if (mpCollider != NULL) {