virsh: Introduce macros to reject mutually exclusive arguments

virsh: Introduce macros to reject mutually exclusive arguments

This patch adds three macros to the virsh source tree that help to
easily check for mutually exclusive parameters.

VSH_EXCLUSIVE_OPTIONS_EXPR has four arguments, two expressions to check
and two names of the parameters to print in the message.

VSH_EXCLUSIVE_OPTIONS is more specific and check the command structure
for the parameters using vshCommandOptBool.

VSH_EXCLUSIVE_OPTIONS_VAR is meant to check boolean variables with the
same name as the parameters.