fixed query cahe resize bug

mysql-test/r/query_cache.result:
  query cache resize bug test
mysql-test/t/query_cache.test:
  query cache resize bug test
sql/set_var.cc:
  typo fixed
sql/sql_cache.cc:
  prevent of using very small (unusable) cache size, that cause problem in memory allocation system (query cache resize bug)

mysql-test/r/query_cache.result

@@ -490,3 +490,19 @@ drop table t1;
 show status like "Qcache_queries_in_cache";
 Variable_name	Value
 Qcache_queries_in_cache	0
+set GLOBAL query_cache_size=1000;
+show global variables like "query_cache_size";
+Variable_name	Value
+query_cache_size	0
+set GLOBAL query_cache_size=1100;
+set GLOBAL query_cache_size=1200;
+set GLOBAL query_cache_size=1300;
+set GLOBAL query_cache_size=1400;
+set GLOBAL query_cache_size=1500;
+set GLOBAL query_cache_size=1600;
+set GLOBAL query_cache_size=1700;
+set GLOBAL query_cache_size=1800;
+set GLOBAL query_cache_size=1900;
+show global variables like "query_cache_size";
+Variable_name	Value
+query_cache_size	1024

mysql-test/t/query_cache.test

@@ -336,3 +336,19 @@ select a from t1;
 show status like "Qcache_queries_in_cache";
 drop table t1;
 show status like "Qcache_queries_in_cache";
+
+#
+# Test of query cache resizing
+#
+set GLOBAL query_cache_size=1000;
+show global variables like "query_cache_size";
+set GLOBAL query_cache_size=1100;
+set GLOBAL query_cache_size=1200;
+set GLOBAL query_cache_size=1300;
+set GLOBAL query_cache_size=1400;
+set GLOBAL query_cache_size=1500;
+set GLOBAL query_cache_size=1600;
+set GLOBAL query_cache_size=1700;
+set GLOBAL query_cache_size=1800;
+set GLOBAL query_cache_size=1900;
+show global variables like "query_cache_size";

sql/set_var.cc

@@ -467,7 +467,7 @@ struct show_var_st init_vars[]= {
   {sys_read_buff_size.name,   (char*) &sys_read_buff_size,	    SHOW_SYS},
   {sys_read_rnd_buff_size.name,(char*) &sys_read_rnd_buff_size,	    SHOW_SYS},
   {sys_rpl_recovery_rank.name,(char*) &sys_rpl_recovery_rank,       SHOW_SYS},
-#ifdef HAVE_QUERTY_CACHE
+#ifdef HAVE_QUERY_CACHE
   {sys_query_cache_limit.name,(char*) &sys_query_cache_limit,	    SHOW_SYS},
   {sys_query_cache_size.name, (char*) &sys_query_cache_size,	    SHOW_SYS},
   {sys_query_cache_type.name, (char*) &sys_query_cache_type,        SHOW_SYS},

sql/sql_cache.cc

@@ -1276,10 +1276,11 @@ ulong Query_cache::init_cache()
   query_cache_size -= additional_data_size;
 
   STRUCT_LOCK(&structure_guard_mutex);
-  if (query_cache_size	<= min_allocation_unit)
+  if (max_mem_bin_size	<= min_allocation_unit)
   {
     DBUG_PRINT("qcache",
-	       (" query_cache_size <= min_allocation_unit => cache disabled"));
+	       (" max bin size (%lu) <= min_allocation_unit => cache disabled",
+		max_mem_bin_size));
     STRUCT_UNLOCK(&structure_guard_mutex);
     goto err;
   }