[8u] RFR 8046044: Fix raw and unchecked lint warnings in XML Signature Impl

[Elliott Baron]

Hi,

I'd like to request a review to backport 8046044 to 8u. The motivation 
for this change is to facilitate backporting "8177334: Update xmldsig 
implementation to Apache Santuario 2.1.1" [1][2].

Original fix:
https://bugs.openjdk.java.net/browse/JDK-8046044
https://hg.openjdk.java.net/jdk9/jdk9/jdk/rev/7d6154df328c

The patch did not apply cleanly to 8u. The rejects were mainly cosmetic, 
with parts of this patch being superseded by 8151893 [3]. Aside from 
fixing file paths, the changes to the original patch are as follows:

src/share/classes/org/jcp/xml/dsig/internal/dom/DOMManifest.java:
src/share/classes/org/jcp/xml/dsig/internal/dom/DOMReference.java:
src/share/classes/org/jcp/xml/dsig/internal/dom/DOMSignedInfo.java:
- Copyright header already updated from 8151893.
src/share/classes/org/jcp/xml/dsig/internal/dom/DOMURIDereferencer.java:
- Copyright header already updated from 8149029.
- Change already applied by 8149029, then later modified by 8151893 [4].
src/share/classes/org/jcp/xml/dsig/internal/dom/DOMPGPData.java:
- Had to modify one line of context affected by 8032733 missing in 8u.
-- 8032733 is fairly large and wide reaching, a backport was previously 
considered and rejected [5].
src/share/classes/org/jcp/xml/dsig/internal/dom/DOMRetrievalMethod.java:
- Copyright header already updated from 8151893.
- One line of context modified due to change in 8151893.

8u webrev:
http://cr.openjdk.java.net/~ebaron/JDK-8046044/webrev.00/

Testing: x86_64 build, jdk_tier1, jdk_security tests

Thanks,
Elliott

[1] https://bugs.openjdk.java.net/browse/JDK-8177334
[2] 
https://mail.openjdk.java.net/pipermail/jdk8u-dev/2019-August/010175.html
[3] https://bugs.openjdk.java.net/browse/JDK-8151893
[4] 
https://hg.openjdk.java.net/jdk/jdk/diff/094bfaa699c3/jdk/src/share/classes/org/jcp/xml/dsig/internal/dom/DOMURIDereferencer.java#l1.12
[5] https://bugs.openjdk.java.net/browse/JDK-8040729