Merge pull request #1160 from he32/shift-overflow-fix

ArenaAlloc/arenaallocimpl.h: avoid shift overflow on 32-bit hosts.

src/third-party/ArenaAlloc/arenaallocimpl.h

@@ -13,6 +13,8 @@
 #include <stdio.h>
 #endif
 
+#include <stdint.h>
+
 namespace ArenaAlloc
 {
 
@@ -108,7 +110,9 @@ namespace ArenaAlloc
       value |= value >> 4;
       value |= value >> 8;
       value |= value >> 16;
+#if SIZE_MAX > UINT32_MAX
       value |= value >> 32;
+#endif
 
       return value + 1;            
     }