RFR (S) 8221325: Add information about swap space to print_memory_info() on MacOS

[Schmelter, Ralf]

Hi David,

> Is offsetof coming from the compiler? Should it be hotspot's offset_of instead?

offsetof would come from <stddef.h> normally, but here offsetof is offset_of. It is redefined in global_definitions_gcc.hpp. 

I've changed to offset_of: http://cr.openjdk.java.net/~rschmelter/webrevs/8221325/webrev.2/ 

Best regards,
Ralf