Add pool support to OSD, part 1

This just fixes all the code so it builds and works like before,
but doesn't yet bring the support for replicated pools.

osd_id.h

@@ -1,4 +1,24 @@
 #pragma once
 
+#define POOL_SCHEME_REPLICATED 1
+#define POOL_SCHEME_XOR 2
+#define POOL_ID_MAX 0x10000
+#define POOL_ID_BITS 16
+#define INODE_POOL(inode) (pool_id_t)((inode) >> (64 - POOL_ID_BITS))
+
+// Pool ID is 16 bits long
+typedef uint32_t pool_id_t;
+
 typedef uint64_t osd_num_t;
 typedef uint32_t pg_num_t;
+
+struct pool_pg_num_t
+{
+    pool_id_t pool_id;
+    pg_num_t pg_num;
+};
+
+inline bool operator < (const pool_pg_num_t & a, const pool_pg_num_t & b)
+{
+    return a.pool_id < b.pool_id || a.pool_id == b.pool_id && a.pg_num < b.pg_num;
+}