Board menu: implement preliminary Party, Bag, Pokegear, and Exit submenus (#11)

macros/code.asm

@@ -11,7 +11,11 @@ ENDM
 ; Design patterns
 
 MACRO jumptable
+if STRIN("\2", "h") == 1
+	ldh a, [\2]
+else
 	ld a, [\2]
+endc
 	ld e, a
 	ld d, 0
 	ld hl, \1

macros/scripts/events.asm

@@ -1065,4 +1065,10 @@ MACRO checksave
 	db checksave_command
 ENDM
 
+	const exitoverworld_command ; $aa
+MACRO exitoverworld
+	db exitoverworld_command
+	db \1 ; exit reason
+ENDM
+
 DEF NUM_EVENT_COMMANDS EQU const_value