RFR: 8301269: Update Commons BCEL to Version 6.7.0

[Joe Wang]

Update Commons BCEL in the JDK from 6.5.0 to 6.7.0. 

1. Improvement
   Code modernization (using relatively more modern language features), normalization (such as naming), javadocs, cleanup and minor improvements made up most of the changes. These changes do not change how BCEL works for the XSLT function in the JDK. Many of the changes unfortunately created long lines, for example merging multiple lines into a single long line, not what we would like to have in the JDK, but I have to leave them as they are so that they don't show up as changes in future updates. 

2. Exclusions
   As it has always been, the focus of the BCEL component is to satisfy the needs for the XSLT functionality. Classes not needed for the JDK are excluded as it has been done previously, this is especially true in the util package. The verifier package is also excluded. Methods and sources that have dependencies on the excluded classes are either removed or modified.

3. Deprecation and Warnings
   
   Deprecated classes and contents relying on them are removed or modified to use proper methods without changing the functionality. Deprecated fields in the original source were changed to private ones in previous update in the JDK, however, since the update process applies sources from the upstream again, they were reverted back. In order to not have to go through them on every update, I'll keep the original source this time. 

    Warnings were one of the main reasons for the changes made to the original source. It has been done in the previous update. In this update, many of the previous JDK fixes on warnings have already been addressed in the upstream source as the result of item 1, thus lessoned the needs to reapply the warning patches. Fixed the rest of warnings as they showed up during build.

4. Note that JRocket specific patches are not in the current code base.

5. Test
    Tier2 tests passed.
    JCK XML tests passed.

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Commit messages:
 - 8301269: Update Commons BCEL to Version 6.7.0

Changes: https://git.openjdk.org/jdk/pull/12464/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12464&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301269
  Stats: 30510 lines in 334 files changed: 9313 ins; 10828 del; 10369 mod
  Patch: https://git.openjdk.org/jdk/pull/12464.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12464/head:pull/12464

PR: https://git.openjdk.org/jdk/pull/12464