* ada-lang.c (discrete_type_high_bound,discrete_type_low_bound): Change

* ada-lang.c (discrete_type_high_bound,discrete_type_low_bound): Change
API to return LONGEST values rather than struct values.
(ada_evaluate_subexp): Change to use new API of discrete_type_low_bound
and discrete_type_high_bound.
(to_fixed_range_type): Create a range type in cases where
argument is base type and its limits are representable as ints.
(ada_is_modular_type): Correct so that base type must be integral.
* ada-lex.l (TRUEKEYWORD,FALSEKEYWORD): Make 'true' and 'false'
keywords when they appear alone, since we are phasing out
direct representation of these identifiers in ebugging data.
* ada-exp.y: Define 'true' and 'false' as primaries.
(type_boolean): New function.
(type_int,type_long,type_long_long,type_floattype_double)
(type_long_double): Remove uses of current_gdbarch for consistency
with type_boolean.
(write_int): Change comment to indicate that it might write boolean
constant as well.
* ada-typeprint.c (ada_print_type): Print '(false, true)' for boolean
type, since will no longer be represented as enumerated type in
debugging data.
* ada-valprint.c (print_optional_low_bound): Handle boolean case
as well.