JDK 9 RFR of 8146041: java.net.URLConnection.guessContentTypeFromStream() does not recognize TIFF streams

[Brian Burkhalter]

Please review at your convenience.

Issue:	https://bugs.openjdk.java.net/browse/JDK-8146041
Patch:	http://cr.openjdk.java.net/~bpb/8146041/webrev.00/

Summary:
Add recognition of TIFF header to guessContentTypeFromStream() and a test to verify that it works.

Note that this change will not be integrated until after the one discussed in http://mail.openjdk.java.net/pipermail/core-libs-dev/2015-December/037832.html has been pushed.

Thanks,

Brian