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

[Erik Joelsson]

Hello,

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/

/Erik