RFR 8173715 (rev2): Remove Flat Profiler

[Gerard Ziemski]

hi all,

The FlatProfiler (i.e. -Xprof) has been deprecated in jdk9, and now it’s the time to remove the code and obsolete the -Xprof flag.

Changes from rev1 to address David’s feedback:

- obsoleted the flag (it’s still accepted, but ignored)
- fixed copyright year in "src/os_cpu/linux_s390/vm/thread_linux_s390.hpp”
- improved comment about the signal based suspend/resume mechanism in "os_*.cpp” files
- removed entire comment from "src/os/solaris/vm/osThread_solaris.hpp"

issue:  https://bugs.openjdk.java.net/browse/JDK-8173715
webrev: http://cr.openjdk.java.net/~gziemski/8173715_rev2_hotspot