1. SMP: Fix an assertion. SMP-specific change accidentally made in non-SMP code

2. Move list of signal actions from the task TCB to the task group.  Signal handlers are a property of the entire task group and not of individual threads in the group.  I know, I preferred it the other way too but this is more compliant with POSIX.

TODO

@@ -1,4 +1,4 @@
-NuttX TODO List (Last updated February 8, 2016)
+NuttX TODO List (Last updated February 18, 2016)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 This file summarizes known NuttX bugs, limitations, inconsistencies with
@@ -25,7 +25,7 @@ nuttx/
   (8)  Graphics subsystem (graphics/)
   (1)  Pascal add-on (pcode/)
   (1)  Build system / Toolchains
-  (3)  Linux/Cywgin simulation (arch/sim)
+  (4)  Linux/Cywgin simulation (arch/sim)
   (4)  ARM (arch/arm/)
 
 apps/
@@ -1620,6 +1620,108 @@ o Linux/Cywgin simulation (arch/sim)
   Status:      Open
   Priority:    Low
 
+  Title:       SMP SIMULATION INCOMPLETE
+  Description: The configuration has basic support SMP testing.  The simulation
+               supports the emulation of multiple CPUs by creating multiple
+               pthreads, each run a copy of the simulation in the same process
+               address space.
+
+               The simulation SMP implemention is incomplete, however.  Two
+               critical SMP functions are not implemented:
+
+                 - int up_cpu_pause(void)
+                 - int up_cpu_resume(void)
+
+               These are used to start a new task on a different CPU:  (1)
+               the other CPU is stopped or paused, (2) the OS datastructures
+               for that CPU are modified, then (2) the other CPU is resumed.
+               Unfortunately, I have not yet thought of a way to implement
+               them in the simulation.
+
+               Currently, for example, you can enable SMP for ostest
+               configuration by enabling:
+
+                 -# CONFIG_EXPERIMENTAL is not set
+                 +CONFIG_EXPERIMENTAL=y
+
+                 +CONFIG_SPINLOCK=y
+                 +CONFIG_SMP=y
+                 +CONFIG_SMP_NCPUS=2
+                 +CONFIG_SMP_IDLETHREAD_STACKSIZE=2048
+
+               And you can enable some additional debug output with:
+
+                 -# CONFIG_DEBUG_SCHED is not set
+                 +CONFIG_DEBUG_SCHED=y
+
+                 -# CONFIG_SCHED_INSTRUMENTATION is not set
+                 +CONFIG_SCHED_INSTRUMENTATION=y
+
+               The result should be as follows:
+
+                 - CPU0 initializes and starts CPU1.  CPU1 is running an
+                   executing the IDLE task.
+
+                   os_start: Entry
+                   os_idletask: CPU1: Beginning Idle Loop
+
+                 - CPU0 brings up the the OS test application on CPU0
+
+                   os_do_appstart: Starting init thread
+                   CPU0: Start init, TCB@42f490, state=5
+                   up_unblock_task: Unblocking TCB=42f490
+                   CPU0: Suspend CPU0 IDLE, TCB@42c180, state=4
+                   CPU0: Resume init, TCB@42f490, state=0
+                   up_unblock_task: New Active Task TCB=42f490
+
+                 - OS test runs and performs some basic checks.
+
+                   stdio_test: write fd=1
+                   stdio_test: Standard I/O Check: printf
+                   stdio_test: write fd=2
+                   stdio_test: Standard I/O Check: fprintf to stderr
+                   ostest_main: putenv(Variable1=BadValue3)
+
+                   up_block_task: Blocking TCB=42f490
+                   CPU0: Suspend init, TCB@42f490, state=4
+                   CPU0: Resume CPU0 IDLE, TCB@42c180, state=3
+                   up_block_task: New Active Task TCB=42c180
+                   up_unblock_task: Unblocking TCB=42f490
+                   CPU0: Suspend CPU0 IDLE, TCB@42c180, state=4
+                   CPU0: Resume init, TCB@42f490, state=0
+                   up_unblock_task: New Active Task TCB=42f490
+
+                   ostest_main: setenv(Variable1, GoodValue1, TRUE)
+                   ostest_main: setenv(Variable2, BadValue1, FALSE)
+                   ostest_main: setenv(Variable2, GoodValue2, TRUE)
+                   ostest_main: setenv(Variable3, Variable3, FALSE)
+                   ostest_main: setenv(Variable3, Variable3, FALSE)
+                   show_variable: Variable=Variable1 has value=GoodValue1
+                   show_variable: Variable=Variable2 has value=GoodValue2
+                   show_variable: Variable=Variable3 has value=GoodValue3
+
+                 - Then OS test tries to start the task ostest on CPU1
+
+                   CPU0: Start ostest, TCB@430e90, state=5
+                   up_unblock_task: Unblocking TCB=430e90
+                   CPU1: Suspend CPU1 IDLE, TCB@42c2c0, state=4
+                   CPU0: Resume ostest, TCB@430e90, state=0
+                   ostest_main: Started user_main at PID=4
+
+               There is no failure but, of course, the task on CPU1 does not
+               run, i.e., it does not replace the IDLE task running on CPU1.
+
+               2016-02-16: The NSH configuration can be forced to run, but
+               only if (1) You don't try to execute built-in commands or to
+               execute commands in the background.  Those thoses cases, it
+               will try to start the command on CPU1 and the same problem
+               as for the ostest case occurs.
+
+               Also, for NSH you have to modify arch/sim/src/up_idle.c so
+               that the IDLE loop only runfs for CPU0.  Otherwise, often
+               simuart_post() will be called from CPU1 and it will try to
+               restart NSH on CPU0 and, again, the same problem occurs.
+
 o ARM (arch/arm/)
   ^^^^^^^^^^^^^^^