RFR: JDK-8302801: Remove fdlibm C sources [v2]

[Joe Darcy]

> While the review of https://github.com/openjdk/jdk/pull/12800 finishes up, I thought I'd get out for the review the next phase of the FDLIBM port: removing the FDLIBM C sources from the repo.
> 
> A repo with the changes for JDK-8302027 and this PR successful build on the default set of platform and successfully run tier 1 tests, which includes tests of the math library.
> 
> There are a few remaining references to the case-independent string "fdlibm" in the make directory and HotSpot sources. HotSpot contains a partial fork for FDLIBM (a tine of FDLIBM?) to use for intrinsics. The remaining make machinery contains logic to determine what set of gcc options can be used for the compile.
> 
> The intention of this change is to remove use of FDLIBM for the core libraries.

Joe Darcy has updated the pull request incrementally with one additional commit since the last revision:

  Respond to review feedback and add description of transliteration process.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12821/files
  - new: https://git.openjdk.org/jdk/pull/12821/files/a1a12347..481af9ad

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12821&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12821&range=00-01

  Stats: 36 lines in 5 files changed: 22 ins; 5 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/12821.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12821/head:pull/12821

PR: https://git.openjdk.org/jdk/pull/12821