RFR: 8253768: Deleting unused pipe_class definitions in adl-file (x86_64.ad).

[Patric Hedlin]

This is just removing some dead/unused code. More importantly, this is a test of the new "issue create" support in
Skara.

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Commit messages:
 - Deleting unused pipe_class definitions in adl-file (x86_64.ad).

Changes: https://git.openjdk.java.net/jdk/pull/74/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=74&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253768
  Stats: 30 lines in 1 file changed: 0 ins; 30 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/74.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/74/head:pull/74

PR: https://git.openjdk.java.net/jdk/pull/74