configs/efm32-dk3650: Support for Energy Micro's development kit for the Leopard Gecko MCU.  From Richard Cochran

You can now specify or override the default board sub-directory.  This is only useful when CONFIG_ARCH_BOARD_CUSTOM is used and the default board sub-directory is not available

Add support for the SO_LINGER socket option.  Based on logic from Jason Jiang.  Utestested on initial commit

NSH: Separate command line parsing from command execution.  Add support for multiple, semicolone separated commands on each line

STM3240G-EVAL: Kernel mode board initialization can't run on the IDLE thread; needs its on initialization kernel thread

NxWM::CTouchscreen: Add CONFIG_NXWM_TOUCHSCREEN_DEVINIT to suppress attempts to initialize the touchscreen from NxWM in the kernel build