resizable namespace.c hashes

* switch allocation to alloc_large_system_hash()
* make sizes overridable by boot parameters (mhash_entries=, mphash_entries=)
* switch mountpoint_hashtable from list_head to hlist_head

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/mount.h b/fs/mount.h
index a17458c..acdb428 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -19,7 +19,7 @@
 };
 
 struct mountpoint {
-	struct list_head m_hash;
+	struct hlist_node m_hash;
 	struct dentry *m_dentry;
 	int m_count;
 };