First part of turning on initial Ada support.

First part of turning on initial Ada support.

* symfile.c (init_filename_language_table): Add extensions for
Ada.
* defs.h (enum language): Add language_ada.
* gdbtypes.h (TYPE_FLAG_FIXED_INSTANCE): Define.
* ada-lang.c: Strip code that is conditionalized out by GNAT_GDB.
(add_symbols_from_enclosing_procs): Make a no-op for now.
(ada_unqualified_name,add_angle_brackets,function_name_from_pc)
(extended_canonical_line_spec, find_sal_from_funcs_and_line)
(find_line_in_linetable, find_next_line_in_linetable)
(read_all_symtabs, is_plausible_func_for_line)
(adjust_pc_past_prologue, error_breakpoint_runtime_sym_not_found)
(is_runtime_sym_defined, check_size): Remove declaration.
(function_name_from_pc, ada_translate_error_message)
(ada_lookup_minimal_symbol): Remove definition.
(ada_add_block_symbols): Remove useless label.
* ada-lang.h (ada_maybe_exception_partial_symbol): Remove
useless declaration.
(ada_is_exception_sym): Likewise.