2003-03-06  Manish Singh  <yosh@gimp.org>

        * configure.in: revised tests for AltiVec. Define ALTIVEC_EXTRA_CFLAGS
        for the extra compiler options needed. Also, support runtime checking
        for AltiVec through the sysctl on Mac OS X, instead of SIGILL assembly
        instruction checking, which needs GNU as.

        * app/base/cpu_accel.c: use the sysctl if available.

        * app/composite/Makefile.am: use ALTIVEC_EXTRA_CFLAGS.

        * app/composite/gimp-composite-altivec.c: conditionally #include
        altivec.h