Fix error in initialize of IDLE TCB due to last change.  The argument list is no long in the TCB, but in the stack.  But not for the IDLE task.  It needs its own mini-argv[] list so that it looks more like other threads.

There used to be two ways to pass parameters to new tasks, depending upon the configuration:  Either (1) argv[] as created as an array with each string strdup'ed.  Or (1) argv[] array and strings were created on the stack before the new task was started.   Now, there is only one way, way (1).  Way (2) might be slightly more compact, but this is not worth carry the complexity of two different ways of doing the same thing.

Obsolete support for the 8051 family.  Trying to maintain compatibility with this family is too much effort and there has never really been a successful NuttX impplementation on these parts

Clean up some kernel build heap allocation issues.  The Cortex-A kernel build now compiles without errors (but cannot link until brk() and sbrk() are implemented).

SAMA5D4-EK:  Add a configuration for testing the kernel build configuration (still a work in progress)