[crac] RFR: Support passing extra options in CREngine [v6]

[Radim Vansa]

> In addition to `-XX:CREngine=program` this adds support to `-XX:CREngine=program,--key,value,--anotherkey` that translates into invoking `program --key value --anotherkey`. Commas support escaping with a backslash.
> 
> This generic parameters support is utilized in `criuengine` that accepts `--verbosity` and `--log-file` options and relays them to `criu`.

Radim Vansa has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains seven commits:

 - Merge branch 'crac' into engine_params
 - Merge branch 'crac' into engine_params
 - Use index var rather than looking up NULLs
 - fixup
 - Do not use dashes
 - Merge branch 'crac' into engine_params
 - Support passing extra options in CREngine

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Changes: https://git.openjdk.org/crac/pull/63/files
 Webrev: https://webrevs.openjdk.org/?repo=crac&pr=63&range=05
  Stats: 157 lines in 5 files changed: 126 ins; 5 del; 26 mod
  Patch: https://git.openjdk.org/crac/pull/63.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/63/head:pull/63

PR: https://git.openjdk.org/crac/pull/63