Otherwise, in locations like virobject.c where PROBE is used,
for certain configure options, the compiler warns:

util/virobject.c:110:1: error: 'intptr_t' undeclared (first use in this function)

As long as we are making this header always available, we can
clean up several other files.

* src/internal.h (includes): Pull in <stdint.h>.
* src/conf/nwfilter_conf.h: Rely on internal.h.
* src/storage/storage_backend.c: Likewise.
* src/storage/storage_backend.h: Likewise.
* src/util/cgroup.c: Likewise.
* src/util/sexpr.h: Likewise.
* src/util/virhashcode.h: Likewise.
* src/util/virnetdevvportprofile.h: Likewise.
* src/util/virnetlink.h: Likewise.
* src/util/virrandom.h: Likewise.
* src/vbox/vbox_driver.c: Likewise.
* src/xenapi/xenapi_driver.c: Likewise.
* src/xenapi/xenapi_utils.c: Likewise.
* src/xenapi/xenapi_utils.h: Likewise.
* src/xenxs/xenxs_private.h: Likewise.
* tests/storagebackendsheepdogtest.c: Likewise.