With it add also a function which can be used in an assert()-like
situation to display the contents of the ring buffer. Within gdb
this call also be called if the program is loaded/still loaded into
memory.
The global variable will be used in a later patch to be accessed from a
python gdb script.
Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
b1f5f8076a