Replace deprecated dependent crates

[tesuji]

Describe the problem you are trying to solve

I suggest to replace deprecated (abandoned) dependent crates like:

• markdown => pulldown_cmark
  Rationale: rustup currently needs to iterate through markdown::Block
  to print content to std{out,err} approriately. But pulldown_cmark
  doesn't provide equivalent methods (only push_html and write_html).

• ole32-sys => winapi
  Rationale: I remove ole32-sys from Cargo.toml and rustup build fine.

• time => chrono
  Rationale: chrono currently use time as dependency itself.

Describe the solution you'd like

Just try to replace them. Build and fix cycle :) .

Notes

Nothing here.

[kinnison]

This sounds emminently sensible and I look forward to reviewing PRs for each in turn :D