RFR: 8295159: DSO created with -ffast-math breaks Java floating-point arithmetic

[Andrew Haley]

A bug in GCC causes shared libraries linked with -ffast-math to disable denormal arithmetic. This breaks Java's floating-point semantics.

The bug is https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55522

One solution is to save and restore the floating-point control word around System.loadLibrary(). This isn't perfect, because some shared library might load another shared library at runtime, but it's a lot better than what we do now. 

However, this fix is not complete. `dlopen()` is called from many places in the JDK. I guess the best thing to do is find and wrap them all. I'd like to hear people's opinions.

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Commit messages:
 - Whitespace
 - 8295159: DSO created with -ffast-math breaks Java floating-point arithmetic
 - 8295159: test cases

Changes: https://git.openjdk.org/jdk/pull/10661/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10661&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295159
  Stats: 193 lines in 5 files changed: 171 ins; 19 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/10661.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10661/head:pull/10661

PR: https://git.openjdk.org/jdk/pull/10661