[Pkg-rust-maintainers] Update of the rand-* crate packages

[Wolfgang Silbermayr]

This is a list of the current status (the ones needing work listed first):

- extprim 1.6.0
  - Depends on rand 0.4, we patched it to depend on 0.5
  - Some work needed to update to rand 0.6
- quickcheck 0.7.2
  - Depends on rand 0.5 and rand_core 0.2
  - Some work needed to update to rand 0.6
  - Upstream is known to be quite responsive
- num-bigint 0.2.2
  - We have 0.2.0, depending on rand 0.5
  - Upstream is on 0.2.2, still depending on rand 0.5
  - Some work needed to update to rand 0.6
- phf-generator 0.7.23
  - We have 0.7.23, depending on rand 0.5
  - Some work needed to update to rand 0.6
- num-complex 0.2.1
  - 0.2.1 is latest, depending on rand 0.5
  - Some work needed to update to rand 0.6

- crossbeam-channel 0.3.4
  - We have 0.3.2
  - 0.3.4 depends on rand 0.6
- jobserver 0.1.12
  - We have 0.1.11, depending on rand 0.5
  - 0.1.12 depends on rand 0.6
- parking-lot-core 0.4.0
  - We have 0.3.1
  - 0.4.0 is latest, depends on rand 0.6
- tempfile 3.0.5
  - We have 3.0.4, depending on rand 0.5
  - Upstream 3.0.5 depends on rand 0.6 already
- tokio-threadpool 0.1.9
  - We have 0.1.7, depending on rand 0.5
  - Upstream 0.1.9 depends on rand 0.6 already
- uuid 0.7.1
  - We have 0.7.1, depending on rand 0.5
  - Upstream git depends on rand 0.6, not yet released