Some final tickless OS bugfixes. No longer EXPERIMENTAL. Update some comments

include/nuttx/arch.h

@@ -970,7 +970,7 @@ int up_prioritize_irq(int irq, int priority);
  *   called early in the initialization sequence by up_intialize().
  *   On return, the current up-time should be available from
  *   up_timer_gettime() and the interval timer is ready for use (but not
- *   actively timing.
+ *   actively timing).
  *
  *   Provided by platform-specific code and called from the architecture-
  *   specific logic.
@@ -1004,7 +1004,7 @@ void up_timer_initialize(void);
  *   when clockid is CLOCK_MONOTONIC.
  *
  *   This function provides the basis for reporting the current time and
- *   also is used to eliminate error build-up from small erros in interval
+ *   also is used to eliminate error build-up from small errors in interval
  *   time calculations.
  *
  *   Provided by platform-specific code and called from the RTOS base code.

include/nuttx/clock.h

@@ -135,7 +135,7 @@
 #define TICK2USEC(tick)       ((tick)*USEC_PER_TICK)                     /* Exact */
 
 #if (MSEC_PER_TICK * USEC_PER_MSEC) == USEC_PER_TICK
-#define TICK2USEC(tick)       ((tick)*MSEC_PER_TICK)                     /* Exact */
+#  define TICK2MSEC(tick)     ((tick)*MSEC_PER_TICK)                     /* Exact */
 #else
 #  define TICK2MSEC(tick)     (((tick)*USEC_PER_TICK)/USEC_PER_MSEC)     /* Rounds */
 #endif

sched/Kconfig

@@ -55,14 +55,14 @@ config ARCH_HAVE_TICKLESS
 config SCHED_TICKLESS
 	bool "Support tick-less OS"
 	default n
-	depends on ARCH_HAVE_TICKLESS && EXPERIMENTAL
+	depends on ARCH_HAVE_TICKLESS
 	---help---
 		Be default, system time is driven by a periodic timer interrupt.  An
 		alternative configurations is a tick-less configuration in which
 		there is no periodic timer interrupt.  Instead and interval timer is
 		used to schedule the next OS time event.  This option selects that
 		tick-less OS option.  If the tick-less OS is selected, then there are
-		additional plaform specific interfaces that must be provided as
+		additional platform specific interfaces that must be provided as
 		defined include/nuttx/arch.h
 
 config USEC_PER_TICK