[crac] RFR: Support passing extra options in CREngine [v4]

[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 incrementally with one additional commit since the last revision:

  Use index var rather than looking up NULLs

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Changes:
  - all: https://git.openjdk.org/crac/pull/63/files
  - new: https://git.openjdk.org/crac/pull/63/files/945e95ed..3cf68256

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=crac&pr=63&range=03
 - incr: https://webrevs.openjdk.org/?repo=crac&pr=63&range=02-03

  Stats: 15 lines in 1 file changed: 3 ins; 4 del; 8 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