"unsupported language" error in info types when using Ada.

This implements a rudimentary version of the la_print_typedef method
for Ada.  Ada usually does not use typedefs, but there is one exception:
pointers to unconstrained arrays.  Without this patch, we sometimes
get an error in the "info types" output:

    (gdb) info types new_integer_type
    All types matching regular expression "new_integer_type":

    File foo.adb:
    Language not supported.

For now, we treat the typedef as if it did not exist - using the
underlying type instead.  This is the right thing to do for most cases,
the only exception being access to array types.  Since we already have
a general issue in handling these pointers (we confuse them with fat
pointers), we will enhance ada_print_typedef to handle these pointers
at the same time we address the general issue.

gdb/ChangeLog:

        * ada-typeprint.c (ada_print_typedef): New function.
        * ada-lang.h (ada_print_typedef): Add declaration.
        * ada-lang.c (ada_language_defn): set la_print_typdef field
        to ada_print_typedef.

gdb/testsuite/ChangeLog:

        * info_types.c, info_types.exp: New files.

Tested on x86_64-linux.

gdb/ada-lang.h

@@ -159,6 +159,9 @@ extern void ada_error (char *); /* Defined in ada-exp.y */
 extern void ada_print_type (struct type *, char *, struct ui_file *, int,
                             int);
 
+extern void ada_print_typedef (struct type *type, struct symbol *new_symbol,
+			       struct ui_file *stream);
+
 extern int ada_val_print (struct type *, const gdb_byte *, int, CORE_ADDR,
                           struct ui_file *, int,
 			  const struct value_print_options *);