tools lib api fs: Add hugetlbfs filesystem detector

Detect hugetlbfs. hugetlbfs__mountpoint() will be used during recording
to help identifying hugetlb mmaps: which should be recognized as anon
mapping.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Reviewed-by: Nilay Vaish <nilayvaish@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Hou Pengyang <houpengyang@huawei.com>
Cc: Zefan Li <lizefan@huawei.com>
Link: http://lkml.kernel.org/r/1473137909-142064-3-git-send-email-wangnan0@huawei.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>