This one's tricker than the VIR_DEBUG0() removal, but the end
result is still C99 compliant, and reasonable with enough comments.

* src/libvirt.c (VIR_ARG10, VIR_HAS_COMMA)
(VIR_DOMAIN_DEBUG_EXPAND, VIR_DOMAIN_DEBUG_PASTE): New macros.
(VIR_DOMAIN_DEBUG): Rewrite to handle one argument, moving
multi-argument guts to...
(VIR_DOMAIN_DEBUG_1): New macro.
(VIR_DOMAIN_DEBUG0): Rename to VIR_DOMAIN_DEBUG_0.