rustdoc: HTML escape crate version

[ollie27]

As --crate-version accepts arbitrary strings they need to be escaped.

r? @GuillaumeGomez

[rust-highfive]

The job x86_64-gnu-llvm-7 of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

2020-02-29T23:48:30.7656068Z ========================== Starting Command Output ===========================
2020-02-29T23:48:30.7659052Z [command]/bin/bash --noprofile --norc /home/vsts/work/_temp/52a7c53f-6511-4298-b3de-a811358cb2bc.sh
2020-02-29T23:48:30.7659337Z 
2020-02-29T23:48:30.7661946Z ##[section]Finishing: Disable git automatic line ending conversion
2020-02-29T23:48:30.7681862Z ##[section]Starting: Checkout rust-lang/rust@refs/pull/69598/merge to s
2020-02-29T23:48:30.7685246Z Task         : Get sources
2020-02-29T23:48:30.7685461Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
2020-02-29T23:48:30.7685707Z Version      : 1.0.0
2020-02-29T23:48:30.7685847Z Author       : Microsoft
---
2020-02-29T23:48:32.0279930Z ##[command]git remote add origin https://github.com/rust-lang/rust
2020-02-29T23:48:32.0290801Z ##[command]git config gc.auto 0
2020-02-29T23:48:32.0299163Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2020-02-29T23:48:32.0305561Z ##[command]git config --get-all http.proxy
2020-02-29T23:48:32.0318760Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/69598/merge:refs/remotes/pull/69598/merge

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[GuillaumeGomez]

Thanks!

@bors: r+ rollup

[bors]

📌 Commit 3c97f8a has been approved by GuillaumeGomez