Fix several minor problems introduced by the memtune series

Fix several minor problems introduced by the memtune series

Add proper documentation to the new VIR_DOMAIN_MEMORY_* macros in
libvirt.h.in to placate apibuild.py.

Mark args as unused in for libvirt_virDomain{Get,Set}MemoryParameters
in the Python bindings and add both to the libvirtMethods array.

Update remote_protocol-structs to placate make syntax-check.

Undo unintended modifications in vboxDomainGetInfo.

Update the function table of the VirtualBox and XenAPI drivers.