target-ppc: Introduce unrealizefn for PowerPCCPU

Use it to clean up the opcode table, resolving a former TODO from Jocelyn.
Also switch from malloc() to g_malloc().

Signed-off-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
e600 core for MPC86xx processors

MPC86xx processors are based on the e600 core, which is not the case
in qemu where it is based on the 7400 processor.

This patch creates the e600 core and instantiates the MPC86xx
processors based on it. Therefore, adding the high BATs and the SPRG
4..7 registers, which are e600-specific [1].

This allows to define the MPC8610 processor too and my program running
on a real MPC8610 target is now able to run on qemu :)

[1] http://cache.freescale.com/files/32bit/doc/ref_manual/E600CORERM.pdf

Signed-off-by: Julio Guerra <guerr@julio.in>
Signed-off-by: Alexander Graf <agraf@suse.de>