[ia64] small integral parameters and return values

[ia64] small integral parameters and return values

This patch fixes a small problem on ia64-hpux when calling functions
whose parameter are small integral values (less than 8 bytes).  In
that case, the parameter value was stored on the wrong side of the
register.  Same problem for return values.

With this patch, the results for gdb.base/callfuncs.exp improve from

        # of expected passes            41
        # of unexpected failures        78

To:

        # of expected passes            95
        # of unexpected failures        24

gdb/ChangeLog:

        * ia64-tdep.c (ia64_struct_type_p): New function.
        (ia64_extract_return_value): Handle integral values that are
        less than 8 bytes long.
        (ia64_push_dummy_call): Likewise.