[foreign-jextract] RFR: Use Windows and Aarch64 LongDouble constants in LayoutUtils

[Jorn Vernee]

Hi,

Please review this small fix that lets LayoutUtils use the new LongDouble constants instead of Double on Windows and Aarch64 to initialize the global `C_LONGDOUBLE` value. Currently the use of Double results in an incorrect ABI attribute, causing a test failure.

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Commits:
 - 9fa0853b: Use new Windows and Aarch64 LongDouble constants in LayoutUtils, instead of Double, which results in the wrong ABI attribute

Changes: https://git.openjdk.java.net/panama-foreign/pull/27/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/27/webrev.00
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/27.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/27/head:pull/27

PR: https://git.openjdk.java.net/panama-foreign/pull/27