RFR: 8276141: XPathFactory set/getProperty method [v2]

[Joe Wang]

> Add setProperty/getProperty methods to the XPath API so that properties can be supported in the future.

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

  Add default impl; Add tests.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6215/files
  - new: https://git.openjdk.java.net/jdk/pull/6215/files/b0b9ae26..569c6cd8

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6215&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6215&range=00-01

  Stats: 205 lines in 5 files changed: 197 ins; 2 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6215.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6215/head:pull/6215

PR: https://git.openjdk.java.net/jdk/pull/6215