RFR: JDK-8062810: Examine src.zip in JDK image and decide if source classes should be organized by module

[Erik Joelsson]

Hello,

Please review this change, which reorganizes src.zip into modules 
directories. It also includes the source of any imported modules into 
src.zip.

If an imported modules contains both sources and classes, the java 
sources are not recompiled, except for module-info.java. This mimics the 
current behavior where an imported module only delivers module-info.java 
in source form.

I changed the definition of the link-file-* macros on Windows to allow 
symlinks to be created there too. In all cases where these are currently 
used, the usage is already conditional on not Windows. I'm then able to 
use the link-file macro to efficiently create a symlinked exploded file 
directory structure for the module based src.zip. In this case, using 
Cygwin symlinks is ok since the zip utility is also Cygwin based and 
will interpret them correctly.

Bug: https://bugs.openjdk.java.net/browse/JDK-8062810

Webrev: http://cr.openjdk.java.net/~erikj/8062810/webrev.01

/Erik