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

Fixes #876

macros/scripts/oam_anims.asm

@@ -0,0 +1,38 @@
+; Battle and sprite OAM animations
+
+MACRO oamframe
+	db \1 ; duration
+	DEF x = \2
+	assert !(x & (1 << (OAM_X_FLIP + 1) | 1 << (OAM_Y_FLIP + 1))), \
+		"oamframe duration overflows into X/Y flip bits"
+	if _NARG > 2
+		rept _NARG - 2
+			DEF x |= 1 << (\3 + 1)
+			shift
+		endr
+	endc
+	db x ; flags
+ENDM
+
+	const_def -1, -1
+
+	const oamend_command ; $ff
+MACRO oamend
+	db oamend_command
+ENDM
+
+	const oamrestart_command ; $fe
+MACRO oamrestart
+	db oamrestart_command
+ENDM
+
+	const oamwait_command ; $fd
+MACRO oamwait
+	db oamwait_command
+	db \1 ; frames
+ENDM
+
+	const oamdelete_command ; $fc
+MACRO oamdelete
+	db oamdelete_command
+ENDM