Networking:  Fix another deadlock condition.  tcp_write_buffer_alloc() calls sem_wait() with network locked.  That worked if CONFIG_NET_NOINTS was not defined because interrupts are automatically restored when the wait happens.  But with CONFIG_NET_NOINTS=y, the wait blocks with the network locked -- bad style and also can lead to a deadlock condition

Networking:  The are issues with the TCP write-ahead buffering if CONFIG_NET_NOINTS is enabled:  There is a possibility of deadlocks in certain timing conditions.  I have not seen this with the Tiva driver that I have been users but other people claim to see the issue on other platforms.  Certainly it is a logic error:  The network should never wait for TCP read-ahead buffering space to be available.  It should drop the packets immediately.

This was fixed by duplicating most of the IOB interfaces:  The versions that waited are still present (like iob_alloc()), but now there are non-waiting verisons of the same interfaces (like iob_tryalloc()).  The TCP read-ahead logic now uses only these non-waiting interfaces.

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

Math library: Adds support for the expm1 functions: http://pubs.opengroup.org/onlinepubs/009695399/functions/expm1.html.  From Brennan Ashton

Networking:  IPv4 and IPv6 work together.  This fixes a bug necessary to accomplish that as well as cleaning up a couple of other issues