Need reviewer - java_crw_demo classfile version assert

[Kelly O'Hair]

Need reviewer.

Change impacts hprof debug version but more importantly
adds two macros to the public #include file classfile_constants.h:

    JVM_CLASSFILE_MAJOR_VERSION
    JVM_CLASSFILE_MINOR_VERSION


6855180: Fix classfile version check in java_crw_demo

http://cr.openjdk.java.net/~ohair/jdk7/6855180-java_crw_demo-classfile/webrev/

-kto