RFR: 8256363: Define toString() for MGF1ParameterSpec [v3]

[Weijun Wang]

> Without this method, `PSSParameterSpec::toString` shows something like:
> MD: SHA-256
> MGF: java.security.spec.MGF1ParameterSpec at 77b52d12
> SaltLength: 32
> TrailerField: 1
> This is ugly.
> 
> Noreg-trivial.

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

  choose a record-style format

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1208/files
  - new: https://git.openjdk.java.net/jdk/pull/1208/files/3b0a4c83..a3ab69e5

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1208&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1208&range=01-02

  Stats: 12 lines in 3 files changed: 1 ins; 2 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1208.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1208/head:pull/1208

PR: https://git.openjdk.java.net/jdk/pull/1208