With this rework, we have two separate per-thread mode flags for
greater flexibility aimed at controlling the debug features on a
per-thread basis:

- T_WOSS can be set to trigger SIGDEBUG upon (unexpected) stage switch
  to in-band mode. This is strictly equivalent to the obsoleted T_WARN
  bit.

- T_WOLI enables/disables the detection of locking inconsistencies
  with mutexes via the EVL_THRIOC_{SET, CLEAR}_MODE interface. This
  combines the former static CONFIG_EVL_DEBUG_MUTEX_INBAND and
  CONFIG_EVL_DEBUG_MUTEX_SLEEP options.

Enabling CONFIG_EVL_DEBUG_WOLI turns on T_WOLI by default for every
new EVL thread running in userland, which can be opted out on a
per-thread basis using EVL_THRIOC_CLEAR_MODE.

Signed-off-by: Philippe Gerum <rpm@xenomai.org>