get_prev_enum_member

get prev constant in the enum
     enum_id - id of enum
     bmask   - bitmask of the constant
               ordinary enums accept only -1 as a bitmask
     value   - value of the current constant
returns: value of a constant with value lower than the specified
         value. -1 no such constants exist.
         All constants are sorted by their values as unsigned longs.

long get_prev_enum_member(long enum_id, long value, long bmask);