Fix VS build.

Add a cast on a double to unsigned assignment.

Change-Id: I4abce7cfa13e145ed0c71469844ac9b274aa1411

vp10/encoder/palette.c

diff --git a/vp10/encoder/palette.c b/vp10/encoder/palette.c
index fd5f402..522e185 100644
--- a/vp10/encoder/palette.c
+++ b/vp10/encoder/palette.c
@@ -49,7 +49,7 @@
                            const uint8_t *indices, int n, int k, int dim) {
   int i, j, index;
   int count[PALETTE_MAX_SIZE];
-  unsigned int rand_state = data[0];
+  unsigned int rand_state = (unsigned int)data[0];
 
   assert(n <= 32768);