[jdk11u-dev] RFR: 8264752: SIGFPE crash with option FlightRecorderOptions:threadbuffersize=30M

[Hui Shi]

Please help review backport of JDK-8264752 related to JFR. 
This backport also includes successive build failure fix JDK-8266206 (for older gcc version).

Applied almost cleanly on jdk11u, except copyright year in license and ClassFileInstaller build/use in test/jdk/jdk/jfr/startupargs/TestBadOptionValues.java.

Tested on Linux X64 tier1/tier2/tier3 release/fastdebug no regression.
New test added in this PR also pass.

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Commit messages:
 - 8264752: SIGFPE crash with option FlightRecorderOptions:threadbuffersize=30M

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/49/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=49&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264752
  Stats: 116 lines in 5 files changed: 101 ins; 0 del; 15 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/49.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/49/head:pull/49

PR: https://git.openjdk.java.net/jdk11u-dev/pull/49