RFR: (S) 7152791 wbapi tests fail on cygwin

[Mikael Gerdin]

Hi all,

Buglink:
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7152791
Webrev:
http://cr.openjdk.java.net/~mgerdin/7152791/webrev.0/

Summary: test/Makefile does not handle cygwin's response to "uname -s" 
and cygwin-style paths.
This caused the test "test/sanity/WBApi.java" to fail because it was 
called through test/Makefile.

To run the test through the makefile one would use a command line like:
cd test; make JT_HOME=$MY_JTREG PRODUCT_HOME=$MY_JDK wbapitest

I modified the Windows detection logic a bit and introduced a 
"GETMIXEDPATH", similar to how the JDK repository handles the same 
issue. I did not modify the "packtest" or "jtreg_tests" targets since 
they aren't executed as far as I know.

Verified the fix by running the makefile target in cygwin manually and 
by running JPRT both with the default "release" and with "-release jdk8"

Thanks
/Mikael