8013531: Provide a utility class in com.sun.tools.classfile to find field/method references

[Mandy Chung]

test/sun/reflect/CallerSensitive/MethodFinder.java is a useful utility 
class that jdeps or other tool can take advantage of. This fix moves 
MethodFinder.java to com.sun.tools.classfile and generalize it to find 
field, method, and interface method references.

Webrev at:
   http://cr.openjdk.java.net/~mchung/jdk8/webrevs/8013531/
thanks
Mandy