Geo: big refactoring of geo.c, zset.[ch] removed.

This commit simplifies the implementation in a few ways:

1. zsetScore implementation improved a bit and moved into t_zset.c where
   is now also used to implement the ZSCORE command.

2. Range extraction from the sorted set remains a separated
   implementation from the one in t_zset.c, but was hyper-specialized in
   order to avoid accumulating results into a list and remove the ones
   outside the radius.

3. A new type is introduced: geoArray, which can accumulate geoPoint
   structures in a vector with power of two expansion policy. This is
   useful since we have to call qsort() against it before returning the
   result to the user.

4. As a result of 1, 2, 3, the two files zset.c and zset.h are now
   removed, including the function to merge two lists (now handled with
   functions that can add elements to existing geoArray arrays) and
   the machinery used in order to pass zset results.

5. geoPoint structure simplified because of the general code structure
   simplification, so we no longer need to take references to objects.

6. Not counting the JSON removal the refactoring removes 200 lines of
   code for the same functionalities, with a simpler to read
   implementation.

7. GEORADIUS is now 2.5 times faster testing with 10k elements and a
   radius resulting in 124 elements returned. However this is mostly a
   side effect of the refactoring and simplification. More speed gains
   can be achieved by trying to optimize the code.

deps/geohash-int/geohash.c

@@ -183,10 +183,6 @@ int geohashDecodeToLatLongWGS84(const GeoHashBits hash, double *latlong) {
     return geohashDecodeToLatLongType(hash, latlong);
 }
 
-int geohashDecodeToLatLongMercator(const GeoHashBits hash, double *latlong) {
-    return geohashDecodeToLatLongType(hash, latlong);
-}
-
 static void geohash_move_x(GeoHashBits *hash, int8_t d) {
     if (d == 0)
         return;

src/Makefile

@@ -117,7 +117,7 @@ endif
 
 REDIS_SERVER_NAME=redis-server
 REDIS_SENTINEL_NAME=redis-sentinel
-REDIS_SERVER_OBJ=adlist.o quicklist.o ae.o anet.o dict.o redis.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o scripting.o bio.o rio.o rand.o memtest.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o geo.o zset.o
+REDIS_SERVER_OBJ=adlist.o quicklist.o ae.o anet.o dict.o redis.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o scripting.o bio.o rio.o rand.o memtest.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o geo.o
 REDIS_GEOHASH_OBJ=../deps/geohash-int/geohash.o ../deps/geohash-int/geohash_helper.o
 REDIS_CLI_NAME=redis-cli
 REDIS_CLI_OBJ=anet.o sds.o adlist.o redis-cli.o zmalloc.o release.o anet.o ae.o crc64.o