8370154: Update @jls and @jvms taglets to point to local specs dir

[dansmithcode]

Updated the JSpec taglets to use relative links into ../specs/jls and ../specs/jvms rather than external links, possible now due to JDK-8370153.

I was surprised there doesn't seem to be a standard way to get a relative path to the docs root, but I copy/pasted from ToolGuide, and made some tweaks based on failures I saw.

Tested with 'make docs' and manually confirmed that a handful of different @jls and @jvms tags are pointing to the right place.

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• JDK-8370154: Update @jls and @jvms taglets to point to local specs dir (Enhancement - P4)

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[mlbridge]

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[liach]

Looks goood. Meanwhile, do you think we should retain external link support via a system property? For the Java SE API specification only distribution for JCP, we might want to link to a static link instead of a local relative link. (I think as long as we can link, a relative link like here is better because it will be stable in the specdiff for JCP review, avoiding spams)

Since we removed the system property jspec.version, we should be able to remove this from the build files too:

jdk/make/Docs.gmk

Line 295 in 066810c

-Djspec.version=$$(VERSION_SPECIFICATION)

[dansmithcode]

JCP reviews actually happen before GA, so I think the external links are always dead anyway?

If it's something the JCP folks care about, I think the right solution is to include JLS & JVMS in the SE-only docs. (They are, after all, specs for Java SE.) But for now, I think the business as usual process is fine.

[dansmithcode]

I'll confirm there are no more uses of jspec.version and update Docs.gmk.

[liach]

I think we can go ahead with this once we verify Oracle's doc build passes. I will approve once the system property passing in Docs.gmk is updated.