RFR: 8193686: Allow --with-jtreg to accept a zip compressed jtreg image

[Erik Helin]

Hi all,

here is small patch that allows the configure option --with-jtreg to 
accept a zip compressed jtreg image (the option currently accepts a 
jtreg image directory). The jtreg image will be unpacked into 
$CONFIGURE_SUPPORT/jtreg.

Patch:
http://cr.openjdk.java.net/~ehelin/8193686/00/

Issue:
https://bugs.openjdk.java.net/browse/JDK-8193686

Testing:
- Tested locally on Linux x86-64 that configuring, building and running
   a jtreg test (via run-test) works with both
   - a jtreg image directory
   - a zip compressed jtreg image
   as values to the --with-jtreg configure option

Thanks,
Erik