PPC64: Add versions of functions in libswscale/input.c optimized for POWER8 VSX SIMD.

This patch addresses Trac ticket #5570. The optimized functions are in file
libswscale/ppc/input_vsx.c. Each optimized function name is a concatenation of the
corresponding name in libswscale/input.c with suffix _vsx.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libswscale/ppc/Makefile

 OBJS += ppc/swscale_altivec.o                                           \
+        ppc/input_vsx.o                                                 \
         ppc/yuv2rgb_altivec.o                                           \
         ppc/yuv2yuv_altivec.o                                           \

libswscale/swscale.c

@@ -566,6 +566,9 @@ static av_cold void sws_init_swscale(SwsContext *c)
 
     ff_sws_init_input_funcs(c);
 
+    if (HAVE_VSX && (!HAVE_BIGENDIAN)) {
+        ff_sws_init_input_funcs_vsx(c);
+    }
 
     if (c->srcBpc == 8) {
         if (c->dstBpc <= 14) {

libswscale/swscale_internal.h

@@ -881,6 +881,7 @@ void ff_get_unscaled_swscale_aarch64(SwsContext *c);
 SwsFunc ff_getSwsFunc(SwsContext *c);
 
 void ff_sws_init_input_funcs(SwsContext *c);
+void ff_sws_init_input_funcs_vsx(SwsContext *c);
 void ff_sws_init_output_funcs(SwsContext *c,
                               yuv2planar1_fn *yuv2plane1,
                               yuv2planarX_fn *yuv2planeX,