FYI: 8243508: Update alpha blending and compositing functions

[Alexey Ushakov]

Corrected FLT_LT and FLT_GE macro
Fixed test/jdk/java/awt/image/DrawImage/IncorrectUnmanagedImageRotatedClip.java failure caused by fix of 8243505

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Commit messages:
 - 8243508: Update alpha blending and compositing functions

Changes: https://git.openjdk.java.net/lanai/pull/40/files
 Webrev: https://webrevs.openjdk.java.net/lanai/40/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8243508
  Stats: 43 lines in 3 files changed: 0 ins; 29 del; 14 mod
  Patch: https://git.openjdk.java.net/lanai/pull/40.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/40/head:pull/40

PR: https://git.openjdk.java.net/lanai/pull/40