Remove support for booting ARTOS images

Pantelis Antoniou stated:
	AFAIK, it is still used but the products using PPC are long gone.
	Nuke it plz (from orbit).

So remove it since it cleans up a usage of env_get_char outside of
the environment code.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/README b/README
index 2cdb268..402ded3 100644
--- a/README
+++ b/README
@@ -3030,8 +3030,8 @@
 
 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
   4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
-  LynxOS, pSOS, QNX, RTEMS, ARTOS;
-  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, ARTOS, LynxOS).
+  LynxOS, pSOS, QNX, RTEMS;
+  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS).
 * Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
   IA64, MIPS, NIOS, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
   Currently supported: ARM, AVR32, Intel x86, MIPS, NIOS, PowerPC).