Don't static_cast literal value

Summary: Use functional style cast on literal value instead of static_cast

Reviewed By: yfeldblum, jdonald

Differential Revision: D19459138

fbshipit-source-id: 103f644322394779fc5cd8512d7a5244d2231091

folly/Conv.cpp

@@ -575,7 +575,7 @@ inline Expected<Tgt, ConversionCode> digits_to(
   UT result = 0;
 
   for (; e - b >= 4; b += 4) {
-    result *= static_cast<UT>(10000);
+    result *= UT(10000);
     const int32_t r0 = shift1000[static_cast<size_t>(b[0])];
     const int32_t r1 = shift100[static_cast<size_t>(b[1])];
     const int32_t r2 = shift10[static_cast<size_t>(b[2])];