A fix and a test case for Bug#9643 " CURSOR_TYPE_SCROLLABLE dos not work"

- check on the client the unsupported feature and return 
an error message if it's been requested.
Additionally added API support for STMT_ATTR_PREFETCH_ROWS.
Post-review fixes.


include/errmsg.h:
  Add a new error code for "Not implemented" client-side error message.
include/mysql.h:
  Add a statement attribute STMT_ATTR_PREFETCH_ROWS - unsigned long
  number of rows to fetch per one COM_FETCH command, used when there
  is a read-only cursor.
  Note, that we don't break compatibility by adding this new member
  because MYSQL_STMT is always allocated inside the client library by
  mysql_stmt_init.
libmysql/errmsg.c:
  Text for the error message CR_NOT_IMPLEMENTED
libmysql/libmysql.c:
  Implement support for STMT_ATTR_PREFETCH_ROWS
  Return an error message on attempt to set an attribute of a prepared
  statement which is not implemented yet. We probably should be doing
  it in the server: currently the server just ignores unknown attributes.
tests/mysql_client_test.c:
  A test case for Bug#9643 "CURSOR_TYPE_SCROLLABLE dos not work"
  - check that an error message is returned for CURSOR_TYPE_SCROLLABLE.
  Additionally, check setting of STMT_ATTR_PREFETCH_ROWS.

include/errmsg.h

@@ -96,6 +96,7 @@ extern const char *client_errors[];	/* Error messages */
 #define CR_NO_DATA                              2051
 #define CR_NO_STMT_METADATA                     2052
 #define CR_NO_RESULT_SET                        2053
-#define CR_ERROR_LAST  /*Copy last error nr:*/  2053
+#define CR_NOT_IMPLEMENTED                      2054
+#define CR_ERROR_LAST  /*Copy last error nr:*/  2054
 /* Add error numbers before CR_ERROR_LAST and change it accordingly. */