RFR: JDK-8296188: Update style and header in JDWP Protocol spec and JVMTI spec

[Jonathan Gibbons]

Please review a simple makefile-only update to inject the standard stylesheet and navigation header into the two JDK specifications that are generated as HTML files in the `gensrc` directory, to bring these docs in line with the rest of the specs documents.

Generated docs at: 
* http://cr.openjdk.java.net/~jjg/8296188/docs.00/specs/jdwp/jdwp-protocol.html
* http://cr.openjdk.java.net/~jjg/8296188/docs.00/specs/jvmti.html

The JVM TI spec has a list of links at the beginning, in bold. This is not a CSS issue ... it is in the HTML, generated by XSL scripts. Ideally, the list should be in a separate `<nav>` element and the `<b>` tags removed, and maybe the style revised using local CSS. But that is a separate issue.

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Commit messages:
 - JDK-8296188

Changes: https://git.openjdk.org/jdk/pull/10957/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10957&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296188
  Stats: 19 lines in 1 file changed: 14 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/10957.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10957/head:pull/10957

PR: https://git.openjdk.org/jdk/pull/10957