AArch64: debug.cpp help() is missing an AArch64 line for pns

When calling debug(), the there is no entry for AArch64.(gdb) call

help()"Executing help"
basic
 pp(void* p) - try to make sense of p
 pv(intptr_t p)- ((PrintableResourceObj*) p)->print()
 ps() - print current thread stack
 pss() - print all thread stacks
 pm(int pc) - print Method* given compiled PC
 findm(intptr_t pc) - finds Method*
 find(intptr_t x) - finds & prints nmethod/stub/bytecode/oop based on pointer into it
 pns(void* sp, void* fp, void* pc) - print native (i.e. mixed) stack trace. E.g.
                  pns($sp, $rbp, $pc) on Linux/amd64 and Solaris/amd64 or
                  pns($sp, $ebp, $pc) on Linux/x86 or
                  pns($sp, 0, $pc) on Linux/ppc64 or
                  pns($sp, $s8, $pc) on Linux/mips or
                  pns($sp + 0x7ff, 0, $pc) on Solaris/SPARC
                - in gdb do 'set overload-resolution off' before calling pns()
                - in dbx do 'frame 1' before calling pns()
misc.
 flush() - flushes the log file
 events() - dump events from ring buffers
compiler debugging
 debug() - to set things up for compiler debugging
 ndebug() - undo debug