BUG#15408: Partitions: subpartition names are not unique

Also, moved some of the code out of handler.h and into partition specific files for better 
separation.
Also, moved some of the C funcs into partition_info as formal C++ methods


mysql-test/r/partition_mgm_err.result:
  result block for test of bug # 15408
mysql-test/t/partition_mgm_err.test:
  test for duplicate subpartition names
sql/Makefile.am:
  adding sql_partition.h, partition_info.cpp, partition_info.h, and partition_element.h to the makefile
sql/ha_partition.cc:
  using the new members of partition_info
sql/ha_partition.h:
  using the new members of partition_info
sql/handler.h:
  moved this code into sql_partition.h
sql/mysql_priv.h:
  including sql_partition.h also now
sql/opt_range.cc:
  using the new members of partition_info
sql/sql_partition.cc:
  moved some of the functions out and into the partition_info class
  using the new members of partition_info
sql/sql_show.cc:
  using the new members of partition_info
win/cmakefiles/sql:
  added partition_info.cpp to the sql cmake file
sql/partition_element.h:
  New BitKeeper file ``sql/partition_element.h''
sql/partition_info.h:
  New BitKeeper file ``sql/partition_info.h''
sql/sql_partition.h:
  New BitKeeper file ``sql/sql_partition.h''

sql/mysql_priv.h

@@ -503,6 +503,8 @@ typedef my_bool (*qc_engine_callback)(THD *thd, char *table_key,
 #include "protocol.h"
 #include "sql_plugin.h"
 #include "sql_udf.h"
+#include "sql_partition.h"
+
 class user_var_entry;
 class Security_context;
 enum enum_var_type