dev: Revert 0a316996de76 [dev, sim: Added missing override...]

This changeset reverts the changset "dev, sim: Added missing override
keywords to fix CLANG compilation (OSX)" which was incorrectly rebased.

Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>

dev, sim: Added missing override keywords to fix CLANG compilation (OSX)

Change-Id: Ice5fa11e77d06576eaa42149f5fa340a769d8b01
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>

misc: Appease clang...again

Once again, clang is having issues with recently committed code.

Unfortunately HSAIL_X86 is still broken.

dev: Add post-fork handling for disk images

This changeset adds support for notifying the disk images that the simulator has
been forked. We need to disable the saving of the CoW disk image from the child
process, and we need to make sure that systems which use a raw disk image are
not allowed to fork to avoid two or more gem5 processes writing to the same disk
image.

Signed-off-by: Andreas Sandberg <andreas@sandberg.pp.se>
[sascha.bischoff@arm.com: Rebased patches onto a newer gem5 version]
Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>

dev: Move storage devices to src/dev/storage/

Move the IDE controller and the disk implementations to
src/dev/storage.