RFR: JDK-8301205: Port fdlibm log10 to Java [v2]

[Joe Darcy]

> Restarting the port of FDLIBM to Java with the log10 method.
> 
> There are two port, the first a near-transliteration from C port to use as a test reference in
> 
> test/jdk/java/lang/StrictMath/FdlibmTranslit.java
> 
> and a more idiomatic Java port in 
> 
> src/java.base/share/classes/java/lang/FdLibm.java
> 
> First I debug the FdlibmTranslit port by running it against the C version. Once that is working, I copy the port into the java.lang.FdLibm.java and do a series of transformation to get the code closer to usual JDK style.

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

  Add comment.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12242/files
  - new: https://git.openjdk.org/jdk/pull/12242/files/17cf431a..0f74dd5f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12242&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12242&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/12242.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12242/head:pull/12242

PR: https://git.openjdk.org/jdk/pull/12242