RFR: 8234741: enhance os::get_core_path on macOS

[Baesken, Matthias]

Hello,

Currently the macOS implementation of os::get_core_path just displays the default core file location.
However it does not handle/show other locations set by the sysctl parameter "kern.corefile" . This is enhanced by this change .
I also take care of  handling %P  which is used a lot for  the  pid-placeholder on macOS in the  "kern.corefile"  parameter .


( additionally  the change  contains a one-liner adjustment in src/java.desktop/macosx/native/libawt_lwawt/awt/AWTView.h  to be able to compile  again  on older macOs versions)


Bug / webrev :

https://bugs.openjdk.java.net/browse/JDK-8234741

http://cr.openjdk.java.net/~mbaesken/webrevs/8234741.0/

Thanks, Matthias