RFR: JDK-8055191: Split GensrcProperties.gmk into separate modules

[Tim Bell]

Hi Erik:

> Please review this change, which splits up GensrcProperties.gmk so 
> that the sources for each module get generated in the correct 
> $module-gensrc target.
>
> I replaced the contents of GensrcProperties.gmk with macros for 
> compiling properties into java files. Then each Gensrc-$module.gmk 
> file includes GensrcProperties.gmk and calls the appropriate macros.
>
> I have verified that the resulting gensrc output dir contains 
> identical java source files as before the change.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8055191
> Webrev: http://cr.openjdk.java.net/~erikj/8055191/webrev.01

Looks good to me-

Tim