Fix: bogus mask on error.h PRINT types

Fix: bogus mask on error.h PRINT types

PRINT_ERR maps to 0x1, PRINT_WARN maps to 0x2, which is fine so far to
use as masks, but PRINT_BUG maps to 0x3, which is the same as both
PRINT_ERR and PRINT_WARN, and does not make sense to use in masks with
__lttng_print:

  (type & (PRINT_WARN | PRINT_ERR | PRINT_BUG))

Fix this by ensuring PRINT_BUG has its own mask, and express all
constants as shifts to eliminate the risk of re-introducing a similar
bug in the future.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>