Update to distinguish from release
fifo: minor documentation clarification
uart: device configuration structure should not be writable
Makefile.common: provide standard sanitized variables for board/device ids
efm32 uart: refactor configuration

The previous solution separated the UART pinmux config from the material
that could be inferred from the peripheral name and instance.  The
pinmuxUART structure didn't really belong in the gpio header, and having
two configuration structures was complex, as was the need to scan for
the correct pinmux config for a given instance.

Replace this with a single and complete configuration structure per
peripheral.  Factor out the common parts shared by all UARTs, and make a
stronger distinction among UART, USART, and LEUART (which will simplify
upcoming SPI support).

The BSPACM UART structure still references this device-specific
configuration, but the default is now a weak reference, theoretically
allowing applications to change the pin configuration without having to
clone periph_cfg.c.  We'll find out if this was a good idea.

This commit addresses the issues for the EFM32GG-STK3700 only.  After
some additional refactoring the remaining boards will be updated.
efm32 uart: update remaining boards to new config interface
tm4c uart: refactor analogously to efm32

Eliminate the separate pinmux configuration in favor of a self-contained
UART configuration structure.
efm32 uart: simplify selection of default UART

Accept BSPACM_CONFIG_DEFAULT_periphname as specifying the default UART.
Also automatically enable it, and propagate the default buffer sizes to
it.
examples: simplify selection of alternative UARTs
efm32: rename peripheral implementation file

This file supports the USART, UART, and LEUART peripherals.  The common
base is USART, and since this file will be responsible for SPI as well
as UART functionality best to make it track the peripheral instead.
efm32: refactor UART/USART device configuration information

Rather than replicate the whole configure function because of structural
differences, make the USART configuration specification an extension of
the UART one.
efm32/button: add example

Basic example for GPIO configuration and interrupt processing.
efm32/adc: add example

Just loops busy-waiting and printing the internal temperature sensor and
voltage once every ten seconds.
efm32/rtc: add example

Loops spending 10 seconds in each supported energy mode.  The clock
source for the RTC can be selected at compile time.
efm32/burtc: add basic demo at 450nA sleep
newlib/fdops: improve default vBSPACMnewlibFDOPSinitializeStdio_ implementation

The previous solution did not attempt to make sure the created handles
corresponded to the correct descriptors.
newlib/uart: provide way to change default console parameters

When the peripheral clock is configured to a low speed the
peripheral-specific defaults may no longer work.  Allow applications
that do this to provide a working configuration.
efm32/power: add example

Uses the Energy Micro load to evaluate power consumption in active mode
at different CPU frequencies.  (Really what it does is demonstrate how
to change CPU frequency among the available options.)
tm4c uart: simplify selection of default UART

Same idea as used in efm32.  Also add pin configurations for the UARTs
on the EK-TM4C1294XL.
tm4c/gpio: provide space for IRQn in pinmux config

This is useful when we're specifying the pin associated with a GPIO
function.