gdbtypes.h: Get rid of the TYPE_FIXED_POINT_INFO macro

gdbtypes.h: Get rid of the TYPE_FIXED_POINT_INFO macro

This is one step further towards the removal of all these macros.

gdb/ChangeLog:

        * gdbtypes.h (struct type) <fixed_point_info, set_fixed_point_info>:
        New methods.
        (INIT_FIXED_POINT_SPECIFIC): Adjust.
        (TYPE_FIXED_POINT_INFO): Delete macro.
        (allocate_fixed_point_type_info): Change return type to void.
        * gdbtypes.c (copy_type_recursive): Replace the use of
        TYPE_FIXED_POINT_INFO by a call to the fixed_point_info method.
        (fixed_point_scaling_factor): Likewise.
        (allocate_fixed_point_type_info): Change return type to void.
        Adjust implementation accordingly.
        * dwarf2/read.c (finish_fixed_point_type): Replace the use of
        TYPE_FIXED_POINT_INFO by a call to the fixed_point_info method.