RFR: JDK-8166202: Tracefile gensrc cannot handle closed src dir in different location

[Erik Joelsson]

The xml/xsl source files used to generate sources for trace in hotspot 
have hard coded relative paths in them that make assumptions on where 
the oracle closed files are located. The source files should not make 
these kind of assumptions since that makes it difficult to change the 
repository layout structure.

While this is mostly an oracle internal change, there are some light 
changes in the open makefile too. The end result should be unchanged.

Bug: https://bugs.openjdk.java.net/browse/JDK-8166202

Webrev: http://cr.openjdk.java.net/~erikj/8166202/webrev.01/

/Erik