RFR: 8266631: StandardJavaFileManager: getJavaFileObjects() impl violates the spec

[Jan Lahoda]

This improves javadoc/specification of several StandardJavaFileManager methods, as requested in these bugs:
https://bugs.openjdk.java.net/browse/JDK-8266631
https://bugs.openjdk.java.net/browse/JDK-8266596
https://bugs.openjdk.java.net/browse/JDK-8266591
https://bugs.openjdk.java.net/browse/JDK-8266590

The CSR is here:
https://bugs.openjdk.java.net/browse/JDK-8268260

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Commit messages:
 - 8266631: StandardJavaFileManager: getJavaFileObjects() impl violates the spec

Changes: https://git.openjdk.java.net/jdk/pull/4360/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4360&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266631
  Stats: 12 lines in 1 file changed: 2 ins; 0 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4360.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4360/head:pull/4360

PR: https://git.openjdk.java.net/jdk/pull/4360