dsp/lossless: workaround gcc-4.8 bug on arm
dsp/lossless: workaround gcc-4.8 bug on arm

and all older versions.
force Sub3() to not be inlined, otherwise the code in Select() will be
incorrect.

extends the check add previously in:
637b3888 dsp/lossless: workaround gcc-4.9 bug on arm

BUG=webp:363

Change-Id: I1403b558f8660b764f3a570a3326822d5ef0be29

webmproject/libwebp,webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,webmproject/libwebp,PKRoma/libwebp,webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,PKRoma/libwebp