Tiva Ethernet:  Move place where interrupts are disabled.  It is probably not possible, but the logic looks like it could leave interrupts disabled

Recent changes to stm32_rtcc.c do not compile with STM32L15XX configurations.  From Jussi Kivilinna.

Disabling any of EXTI 5-9 interrupts was disabling interrupts for all EXTI 5-9. Same issue with EXTI 10-15.  From Jussi Kivilinna.

Get USART 2 & 3 working on lpc4357-evb. These changes are required to get USART 2 and 3 working on the Embest development board.  From Toby Duckworth

Remove CONFIG_DEBUG_STACK.  Adding CONFIG_STACK_COLORATION makes this configuration option pointless

Add CONFIG_STACK_COLORATION that does the same thing as CONFIG_DEBUG_STACK but without enabling debug.  From David Sidrane

Armv7-M: Remove Px4-only setting of stack to 0xff.  This is incompatible with standard NuttX stack montitoring logic

Armv7-M: Remove Px4-only setting of stack to 0xff.  This is incompatible with standard NuttX stack montitoring logic

All Ethernet drivers (again):  Missed one place where arp_out() is called and neighber_out() needs to be called

Networking:  Modify all Ethernet drivers:  Do neighbor look-up on all outgoing IPv6 packs in order to properly set the destination link layer address.

nuttx/arch/arm/src/stm32/stm32_serial.c: fix declaration and definition of up_receive() and up_dma_receive() to match fields of uart_ops_s from nuttx/include/nuttx/serial/serial.h

Tiva Ethernet:  When calling into the stack from the worker thread, it is necessary to have the stack locked

Networking:  All Ethernet drivers:  Call ipv6_input if IPv6 is enabled and an IPv6 packet is received

- Copy net/devif/devif_input.c to ipv6_input.c.  Remove all IPv4-specific logic.
- Rename net/devif/devif_input.c to ipv4_input.c.  Remove all IPv6-specific logic
- Split IPv4 header structure out as net_ipv4hdr_s from net_iphdr_s

Removed setting of the initial timer interval load value (or, rather, it is always set to zero for a free-running timer).  Also, do not unconditional enable the timer out interrupt.  The timerout interrupt is not not enabled until tiva_timer32_setinterval() is called.

Timer Timer:  Timer driver now initializes without complaints.  Need a test driver of some kind to make more testing progress.