RFR: 8266950: Remove vestigial support for non-strict floating-point execution

[David Holmes]

As part of JEP 306, the vestiges of HotSpot support for non-strict floating-point execution can be removed. All methods implicitly have strictfp semantics so the explicit checks for is_strict() can be replaced by true and the code reformulated accordingly.

There are still some names that include "strict" that could potentially be renamed to remove it, but the fact we have to have strict fp semantics is still important on some platforms, so the names help reinforce that IMO.

Testing: tiers 1-3

Thanks,
David

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Commit messages:
 - Removed divDPR_reg_round as it has a false predicate and so is now unused
 - Revert classFileParser changes as they will be handled by JDK-8266530
 - 8266530: HotSpot changes for JEP 306

Changes: https://git.openjdk.java.net/jdk/pull/3991/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3991&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266950
  Stats: 203 lines in 27 files changed: 4 ins; 153 del; 46 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3991.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3991/head:pull/3991

PR: https://git.openjdk.java.net/jdk/pull/3991