RFR: JDK-8280373: Update Xalan serializer / SystemIDResolver to align with JDK-8270492 [v3]

[Matthias Baesken]

> After 8270492
> https://github.com/openjdk/jdk/commit/78b2c8419bc69436873e6fc9c542480949d140c5
> has been pushed, we should adjust src/java.xml/share/classes/com/sun/org/apache/xml/internal/serializer/utils/SystemIDResolver.java getAbsoluteURI to what has been done in 8270492 to src/java.xml/share/classes/com/sun/org/apache/xml/internal/utils/SystemIDResolver.java

Matthias Baesken has updated the pull request incrementally with one additional commit since the last revision:

  Add LastModified

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7155/files
  - new: https://git.openjdk.java.net/jdk/pull/7155/files/8f2169cb..69584e8f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7155&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7155&range=01-02

  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7155.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7155/head:pull/7155

PR: https://git.openjdk.java.net/jdk/pull/7155