Try printing array range using the name of its index type

Try printing array range using the name of its index type

   type Char_Table is array (Character range Character'First .. Character'Last)
     of Natural;

Trying to print the type description of this type currently yields:

   (gdb) ptype char_table
   type = array ('["00"]' .. '["ff"]') of natural

Although technically correct, it seemed more useful to print the array
range as:

   (gdb) ptype char_table
   type = array (character) of natural

This patch implements this suggestion.

gdb/ChangeLog:

        * ada-typeprint (type_is_full_subrange_of_target_type):
        New function.
        (print_range): Add parameter bounds_prefered_p.  If not set,
        try printing range types using the name of their base type.
        (print_range_type): Add parameter bounds_prefered_p.
        Use it in call to print_range.
        (print_array_type, ada_print_type): Update calls to print_range
        and print_range_type.

gdb/testsuite/ChangeLog:

        * gdb.ada/array_char_idx: New testcase.