RFR: 8266542: Remove broken -XX:-UseLoopSafepoints flag

[Tobias Hartmann]

Simply running `java -XX:-UseLoopSafepoints` already asserts and more sophisticated testing triggers all kinds of asserts and crashes in various places. [JDK-6232281](https://bugs.openjdk.java.net/browse/JDK-6232281) made an attempt of fixing a common case. I had a quick look on what it would take to fix all cases and it's definitely non trivial. Also, we would need to make sure that new optimizations work without safepoints in loops. I don't see much value in keeping the flag for debugging either because disabling safepoints in loops has massive side-effects on other optimizations.

I therefore propose to remove the flag.

Thanks,
Tobias

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Commit messages:
 - Forgot to remove }
 - 8266542: Remove broken -XX:-UseLoopSafepoints flag

Changes: https://git.openjdk.java.net/jdk/pull/3871/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3871&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266542
  Stats: 57 lines in 5 files changed: 1 ins; 47 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3871.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3871/head:pull/3871

PR: https://git.openjdk.java.net/jdk/pull/3871