Split "gfx anims" into "pic anims" and "sprite anims"

Fixes #876

macros/scripts/pic_anims.asm

@@ -0,0 +1,28 @@
+MACRO frame
+	if _NARG <= 2
+		db \1 ; index
+		db \2 ; duration
+	else
+	; LEGACY: Support for the old name of "oamanim"
+		oamanim \#
+	endc
+ENDM
+
+	const_def -1, -1
+
+	const endanim_command ; $ff
+MACRO endanim
+	db endanim_command
+ENDM
+
+	const setrepeat_command ; $fe
+MACRO setrepeat
+	db setrepeat_command
+	db \1 ; amount of times to repeat
+ENDM
+
+	const dorepeat_command ; $fd
+MACRO dorepeat
+	db dorepeat_command
+	db \1 ; command offset to jump to
+ENDM