RFR: JDK-8145180: Add back PrintGC, PrintGCDetails and -Xloggc

[Bengt Rutisson]

Hi everyone,

Could I have a couple of reviews for this follow-up change to the GC 
logging changes for the unified logging framework?

http://cr.openjdk.java.net/~brutisso/8145180/webrev.00/
https://bugs.openjdk.java.net/browse/JDK-8145180

The change adds back the flags PrintGC and PrintGCDetails as well as 
-Xloggc. I've tried to keep the behavior similar to before, so if 
-Xloggc is used the PrintGC and PrintGCDetails settings should affect 
what is logged to the file not to stdout.

The change also adds warning messages for all three flags that will let 
the users know that the flags have been deprecated.

I've tried to add this code back in similar places where the code used 
to be. I've put PrintGC and PrintGCDetails back in globals.hpp at the 
same place where they used to be. I've added a method, 
handle_deprecated_print_gc_flags(), which is called from the place in 
Arguments::parse() where we used to enable PrintGC if PrintGCDetails was 
enabled 
(http://hg.openjdk.java.net/jdk9/hs-rt/hotspot/rev/f944761a3ce3#l134.259). 
I also re-introduce the Arguments::_gc_log_filename variable to hold the 
file name specified by -Xloggc.

Thanks,
Bengt