Prepared statements in embedded server
Several changes in library code with two goals:
to make mysql_prepare_stmt working in embedded server
to get rid of #define mysql_interface_func mysql->methods->interface_func
in user's interface


include/mysql.h:
  modifications of interface
  two goals: to implement prepared statements and to get rid
  of #define mysql_proc (mysql->smth) in interface
include/sql_common.h:
  read_rows function got 'virtual'
libmysql/client_settings.h:
  interface of some functions declared in client.c moved here
libmysql/libmysql.c:
  several functions changed with declared goals
libmysqld/embedded_priv.h:
  libmysqld.c <--> lib_sql.cc interface moved here
libmysqld/lib_sql.cc:
  all embedded 'virtual' functions moved here so they can be static
libmysqld/libmysqld.c:
  embedded 'virtual' function was moved out of here
sql-common/client.c:
  several changes with the declared goal
sql/sql_class.h:
  place to store statement data added to THD
sql/sql_prepare.cc:
  storing of prepare_statement result for embedded server added