Cleanup HOST_LONG_BITS, HOST_I386 and HOST_X86_64

HOST_LONG_BITS is now computed automatically in
include/qemu-common.h so remove all the configuration/probing
that was required before this patch to get the correct value.

Also get rid of HOST_I386 and HOST_X86_64 since they are not
needed anymore.

Change-Id: I61823a896033e38938346242b7aea78d3e832826
11 files changed