cast string to uint64 and uint32 failed on arm32

[jinlinGuan]

cast max uint32 string to uint32:
cast.ToUint32E("4294967295") returns 0 and err: unable to cast "4294967295" of type string to uint32

cast max uint64 string to uint64:
cast.ToUint64E("18446744073709551615") returns 0 and err: unable to cast "18446744073709551615" of type string to uint64

The cases above work fine in v1.4.1.