sse-fixups: use more portable functions to help compile with clang

Original patch found here
http://www.freebsd.org/cgi/cvsweb.cgi/ports/x11/babl/files/patch-sse-fixups.c?rev=1.1;content-type=text%2Fplain

CVS tags: RELEASE_8_3_0, HEAD

Fix the build with clang.

PR:		ports/163518
Submitted by:	Jan Beich <jbeich@tormail.net>
Feature safe:	yes