Constants for message types

Instead of declaring constants in reports to manage message types, save time and use attributes of interface IF_XO_CONST_MESSAGE  :

IF_XO_CONST_MESSAGE=>ABORT     " TYPE BAPI_MTYPE  'A'
IF_XO_CONST_MESSAGE=>ERROR     " TYPE BAPI_MTYPE  'E'
IF_XO_CONST_MESSAGE=>EXIT      " TYPE BAPI_MTYPE  'X'
IF_XO_CONST_MESSAGE=>INFO      " TYPE BAPI_MTYPE  'I'
IF_XO_CONST_MESSAGE=>SUCCESS   " TYPE BAPI_MTYPE  'S'
IF_XO_CONST_MESSAGE=>WARNING   " TYPE BAPI_MTYPE  'W'