RFR: 8182758: Remove the Native-Header Generation Tool (javah)

[Jonathan Gibbons]

Please review a fix to remove the javah tool, as previously advertised
in JDK-8152360. (The replacement is to use the javac -h option.)

Not surprisingly, most of this is removing code, with just a couple of src/
files being modified, as well as some tests.

JBS: https://bugs.openjdk.java.net/browse/JDK-8182758
Webrev: http://cr.openjdk.java.net/~jjg/8182758/webrev.00/

-- Jon