Mark xmm6 and xmm7 as clobbered in ff_vp3_idct_sse2(), which is contributing

to the VP6 fate failures on Win64.

Originally committed as revision 24931 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/x86/vp3dsp_sse2.c

@@ -171,6 +171,7 @@ void ff_vp3_idct_sse2(int16_t *input_data)
         VP3_1D_IDCT_SSE2(ADD8, SHIFT4)
         PUT_BLOCK(%%xmm0, %%xmm1, %%xmm2, %%xmm3, %%xmm4, %%xmm5, %%xmm6, %%xmm7)
         :: "r"(input_data), "r"(ff_vp3_idct_data), "m"(ff_pw_8)
+        : "%xmm6", "%xmm7"
     );
 }