8044034: Remove unused com/sun/tools/hat files

[Mandy Chung]

These files are not used in the jdk repository and it'd be a good 
cleanup to remove them:

jdk/src/share/classes/com/sun/tools/hat/MANIFEST.mf
jdk/src/share/classes/com/sun/tools/hat/README.txt
jdk/src/share/classes/com/sun/tools/hat/build.xml
https://bugs.openjdk.java.net/browse/JDK-8044034

Webrev:
http://cr.openjdk.java.net/~mchung/jdk9/webrevs/8044034/webrev.00/

Mandy