add array_count.h (#2514)

src/n64dd/n64dd_801C8000.c

@@ -1,5 +1,8 @@
 // Does some command processing
+
 #include "n64dd.h"
+
+#include "array_count.h"
 #include "versions.h"
 #include "z_locale.h"
 

src/n64dd/n64dd_801CA0B0.c

@@ -1,6 +1,8 @@
 #include "n64dd.h"
+
 #include "libc64/aprintf.h"
 #include "attributes.h"
+#include "array_count.h"
 
 #include "global.h"
 

src/n64dd/z_n64dd.c

@@ -1,11 +1,14 @@
 // Main interface for the 64DD from the rest of the game. Starts background
 // threads and provides functions to submit commands to them.
+
+#include "n64dd.h"
+
 #include "libc64/sleep.h"
+#include "array_count.h"
 #include "fault.h"
 #include "gfx.h"
 #include "irqmgr.h"
 #include "line_numbers.h"
-#include "n64dd.h"
 #include "stack.h"
 #include "stackcheck.h"
 #include "sys_freeze.h"