Make CPC version run from ROM

This frees up an extra 11K of RAM for apps.

It is still slightly broken: glitches during start of the ROM, and the
desktop icons are somehow missing. I don't know why yet...
diff --git a/contiki-cpc/Makefile.cpc b/contiki-cpc/Makefile.cpc
index 49b5ce7..d2b3c68 100644
--- a/contiki-cpc/Makefile.cpc
+++ b/contiki-cpc/Makefile.cpc
@@ -102,8 +102,7 @@
 	$(LD) -f arch/contiki.lnk
 	#./bin/make_labels contiki.map arch/contiki_labels.s
 	sed -n "/^_CODE\|^_DATA\|_INITIALIZED/,/^Area/ s/^     \([0-9A-F]*\)  \([^ ]*\) .*/ \2 == 0x\1/p" contiki.map > arch/contiki_labels.s
-	makebin -p -s 65535 < contiki.ihx > contiki.raw
-	dd if=contiki.raw of=contiki.bin bs=256 skip=1
+	makebin -p -s 65536 -o 0xC000 < contiki.ihx > contiki.bin
 	cpcfs contiki.dsk f
 	cpcfs contiki.dsk p contiki.bin,256,256 -b -e