[crac] RFR: 8273607: Import crac/jdk [v2]

[Anton Kozlov]

> Import the initial CRaC prototype. The PR targets `crac` branch where it will live, while `master` is automatically synced to `openjdk/master`. The initial implementation is based on jdk-14-ga. After the integration, I'm going to merge the latest promotion build from the `master` branch.
> 
> Please feel free to leave comments. I'll try to resolve simple issues or will record more complex ones.

Anton Kozlov has updated the pull request incrementally with four additional commits since the last revision:

 - Revert "8238380: java.base/unix/native/libjava/childproc.c "multiple definition" link errors with GCC10"
   
   This reverts commit 5753cadf8e449cd61ec100bac0e30b44f2c4bea4.
 - Revert "8238388: libj2gss/NativeFunc.o "multiple definition" link errors with GCC10"
   
   This reverts commit 7dcc6fa5620824ac72aabea54fb8459c552d093c.
 - Revert "8238386: (sctp) jdk.sctp/unix/native/libsctp/SctpNet.c "multiple definition" link errors with GCC10"
   
   This reverts commit d9688feedc73c68f4023df37332f093bd3b3143a.
 - Revert "8237879: make 4.3 breaks build"
   
   This reverts commit 24b5e247c747fa08275861cadf1898d6458c3860.

-------------

Changes:
  - all: https://git.openjdk.java.net/crac/pull/1/files
  - new: https://git.openjdk.java.net/crac/pull/1/files/d5c4d836..a5f81699

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=crac&pr=1&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=crac&pr=1&range=00-01

  Stats: 30 lines in 7 files changed: 0 ins; 12 del; 18 mod
  Patch: https://git.openjdk.java.net/crac/pull/1.diff
  Fetch: git fetch https://git.openjdk.java.net/crac pull/1/head:pull/1

PR: https://git.openjdk.java.net/crac/pull/1