list: Define new API virStorageListAllStoragePools

list: Define new API virStorageListAllStoragePools

This introduces a new API to list the storage pool objects,
4 groups of flags are provided to filter the returned pools:

  * Active or not

  * Autostarting or not

  * Persistent or not

  * And the pool type.

include/libvirt/libvirt.h.in: New enum virConnectListAllStoragePoolFlags;
                              Declare the API.
python/generator.py: Skip the generating
src/driver.h: (virDrvConnectListAllStoragePools)
src/libvirt.c: Implementation for the API.
src/libvirt_public.syms: Export the symbol.