* 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

* Fix 6-byte multichar literals

* Add `struct` to `e_ga_class::ga_s`

* Fix remaining wrong forward declares (struct/class)

* Replace `#include <string>` with `#include <cstring>`

* Guard FLT_EPSILON define to prevent redefinition

* Add missing `#include <cstring>` for direct cstring function usage

* some wii OS fixes

* remove old dol2asm comments

* remove dol2asm.h

* remove function address comments

* normalize ATTRIBUTE_ALIGN usage

* DECL_WEAK macro

* fix gcc attribute weak macro

* wrap more mwcc specific things in ifdefs

* fixes

* fix revo sdk version flags

* fixes

* Fix JUT_ASSERT to be a nested define

* Switch names that appear in asserts to be constants instead of defines

* Replace `0` in asserts with `NULL` or `FALSE`

* Fix fpclassify

* Fix ARRAY_SIZE

* Use G_CM3D_F_INF

* More fixes for fpclassify

* Remove FLOAT_LABEL

* Remove incorrect FLAG_ON macro

* Remove UNK_BSS macro

* Silence clangd unused header warning for PCH

* Fix spurious differences when using ninja diff

* Fix some clangd errors/warnings

* switch to dtk setup

* some cleanup / fixes

* cleanup d_a_alink literals

* Restore doxygen, update CI & README.md (#1)

* Fix build image ref (#2)

---------

Co-authored-by: Luke Street <luke@street.dev>