SAMA5D3/4:  More renaming.  Change SAMA5D3 EMAC to EMACA and SAMA5D4 to EMACB so that the configuration and build system can configure them.  I might come up with something better later

SAMA5:  Back out most of commit c37b5b7b97d0644743c04f2c3d9e2b7ef9f5d698.  Things are going to have to be done differently

SAMA5:  Rename most EMAC definitions to EMAC0 to handle the SAMA5D4 which has to EMAC modules and no GMAC

Create P-Code execution helper in apps/interpreters/prun; The P-Code binary format is functional except that there are still some modularity and kernel build issues that need to be addressed.

Add serial method so that lower half driver can provide RX flow control information.  From Jussi Kivilinna

STM32: Fix STM32F100CB pin configuration (from Kosma Moczek); and make chip naming a little more consistent

Nucleo-F401RE:  With these changes and the changes from previous commits, the basic Nucleo-F401RE NSH configuration is working.

The Nucleo-F401RE has no on-board cystal and, hence, must use the on-chip HSI oscillator for the PLL include clock