Add a new config macro CONFIG_PARAVIRT which defaults to be defined on
x86. This is the first step for supporting a HVMlite Mini-OS.
Doing this via CONFIG_PARAVIRT instead of something like CONFIG_HVMLITE
was chosen as the arm port can then drop some dummy routines needed for
para-virtualization only.
Add include/paravirt.h for future support of paravirt specific
handling.
Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>