Core modification and listing kernel event support

Core modification and listing kernel event support

File descriptor sent to the kconsumerd are now sent one at a time. The
problem was that there is a maximum packet size once the control buffer
is used with recvmsg/sendmsg. This upper bound can be read and set at :
/proc/sys/net/core/optmem_max.

Also, the kconsumerd execlp is set to verbose at this time for debugging
purpose.

Introduce --list-events to list all kernel events with the -k option
added. NOT supported for user-space at this point.

Signed-off-by: David Goulet <david.goulet@polymtl.ca>