S390: Silence gcc 5.1 array-bounds warnings if build with -O3.

[Andreas Schwab]

Stefan Liebler <stli@linux.vnet.ibm.com> writes:

> The gcc 5.1 reports some "array subscript is above array bounds"
> warnings if compiled with -O3 on s390x. There are no warnings with -O2.
> Older or newer GCCs do not report these warnings.

If they are bugs in just a single (obsolete) version of gcc then we
shouldn't clutter the source just for that version.  Those that are
affected can always use --disable-werror.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."