RFR: 8303799: [BACKOUT] JDK-8302801 Remove fdlibm C sources

[David Holmes]

This reverts commit b5b5cba7feb0e7ef957fd6bef1e591fdb6fdaa9f.

Thanks.

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Commit messages:
 - Revert "8302801: Remove fdlibm C sources"

Changes: https://git.openjdk.org/jdk/pull/12916/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12916&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303799
  Stats: 6643 lines in 65 files changed: 6613 ins; 20 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/12916.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12916/head:pull/12916

PR: https://git.openjdk.org/jdk/pull/12916