arrow

ARROW-5541 [R]: cast from negative int32 to uint32 and uint64 are now safe

Minor test update:

``` r
library(arrow, warn.conflicts = FALSE)

a <- array(-(1:10))
a$cast(uint32())
#> Error in Array__cast(self, target_type, options): Invalid: Integer value out of bounds
a$cast(uint64())
#> Error in Array__cast(self, target_type, options): Invalid: Integer value out of bounds
```

<sup>Created on 2019-06-10 by the [reprex package](https://reprex.tidyverse.org) (v0.3.0.9000)</sup>

Author: Romain Francois <romain@rstudio.com>

Closes #4509 from romainfrancois/ARROW-5541/update_tests and squashes the following commits:

0657e688 <Romain Francois> test updates now that C++ cast is safe