Make hash table algorithm selectable

jenkins hash is old. Lets try murmur3 to start! Default is the old one, so
people aren't surprised.

Author: dormando

Makefile.am

@@ -10,6 +10,8 @@ timedrun_SOURCES = timedrun.c
 
 memcached_SOURCES = memcached.c memcached.h \
                     hash.c hash.h \
+                    jenkins_hash.c jenkins_hash.h \
+                    murmur3_hash.c murmur3_hash.h \
                     slabs.c slabs.h \
                     items.c items.h \
                     assoc.c assoc.h \

assoc.c

@@ -218,7 +218,7 @@ static void *assoc_maintenance_thread(void *arg) {
             for (it = old_hashtable[expand_bucket]; NULL != it; it = next) {
                 next = it->h_next;
 
-                bucket = hash(ITEM_key(it), it->nkey, 0) & hashmask(hashpower);
+                bucket = hash(ITEM_key(it), it->nkey) & hashmask(hashpower);
                 it->h_next = primary_hashtable[bucket];
                 primary_hashtable[bucket] = it;
             }

doc/protocol.txt

@@ -559,6 +559,7 @@ other stats command.
 | hashpower_init    | 32       | Starting size multiplier for hash table      |
 | slab_reassign     | bool     | Whether slab page reassignment is allowed    |
 | slab_automove     | bool     | Whether slab page automover is enabled       |
+| hash_algorithm    | char     | Hash table algorithm in use                  |
 |-------------------+----------+----------------------------------------------|