RFR: 8276571: C2: pass compilation options as structure

[Vladimir Kozlov]

Currently we pass several compilation options as separate arguments to `Compile`: 

Compile C(env, target, entry_bci, subsume_loads, do_escape_analysis, eliminate_boxing, do_locks_coarsening, install_code, directive); 

Originally we had only `subsume_loads` option but we added few since then and we may add more. 

I suggest to add new `Options` class to pass these values into `Compile`.

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Commit messages:
 - 8276571: C2: pass compilation options as structure

Changes: https://git.openjdk.java.net/jdk/pull/6237/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6237&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8276571
  Stats: 66 lines in 4 files changed: 30 ins; 15 del; 21 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6237.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6237/head:pull/6237

PR: https://git.openjdk.java.net/jdk/pull/6237