Implement warning diagnostic flags for RGBFIX (#1766)

* Implement warning diagnostic flags for RGBFIX

* `-m/--mbc-type help` prints to stdout

* Support `-m list` as well as `-m help`

* Make invalid `rgbfix -l` characters a fatal error, like other invalid CLI arguments

* Refactor fix/main.cpp into multiple files

src/CMakeLists.txt

@@ -72,6 +72,8 @@ set(rgblink_src
 
 set(rgbfix_src
     "fix/main.cpp"
+    "fix/mbc.cpp"
+    "fix/warning.cpp"
     )
 
 set(rgbgfx_src