relax alignment of Cent for 32 bit targets

Author: WalterBright

src/core/int128.d

@@ -18,7 +18,10 @@ alias I = long;
 alias U = ulong;
 enum Ubits = uint(U.sizeof * 8);
 
-align(16) struct Cent
+version (X86_64) private enum Cent_alignment = 16;
+else             private enum Cent_alignment = (size_t.sizeof * 2);
+
+align(Cent_alignment) struct Cent
 {
     U lo;      // low 64 bits
     U hi;      // high 64 bits