suppress MS compiler complaint about negating unsigned (closes #330)

src/util/sobolseq.c

@@ -93,7 +93,12 @@ static unsigned rightzero32(uint32_t n)
     const uint32_t a = 0x05f66a47;      /* magic number, found by brute force */
     static const unsigned decode[32] = { 0, 1, 2, 26, 23, 3, 15, 27, 24, 21, 19, 4, 12, 16, 28, 6, 31, 25, 22, 14, 20, 18, 11, 5, 30, 13, 17, 10, 29, 9, 8, 7 };
     n = ~n;                     /* change to rightmost-one problem */
-    n = a * (n & (-n));         /* store in n to make sure mult. is 32 bits */
+#ifdef _MSC_VER
+#pragma warning(suppress:4146)
+    n = a * (n & (-n)); /* same as below, but suppress spurious warning/error with MS compiler about negating unsigned int */
+#else
+    n = a * (n & (-n)); /* store in n to make sure mult. is 32 bits */
+#endif      
     return decode[n >> 27];
 #endif
 }