Ncurses-based CTK backend for the native platform.
ctk-curses: Add mouse support to the ncurses CTK backend.
ctk-curses: Cleanup + fixes

* Cleanup
* Fix warnings
* Fix indentation
* Only wait 1ms for keyboard timeout
* Hide text cursor
* Pump mouse events just in case
* Add F9 as menu key since F10 is used as menu trigger by Gnome
ctk-curses: fix build

Including curses.h in contiki-conf.h (required for COLOR_* defines)
induced a symbol name clash with neighbor-attr.c on "timeout".

Renamed timeout to neighbor_timeout.
ctk-curses: Enable screensaver
ctk-curses: Add configuration for various apps
ctk-curses: Cleanup
core/lib/settings: Generalized Settings Manager to work on any platform

This commit moves the Settings Manager from the AVR codebase
into the Contiki core library. Any platform that implements
the Contiki EEPROM API can now use the Settings Manager's
key-value store for storing their persistent configuration info.

The Settings Manager is a EEPROM-based key-value store. Keys
are 16-bit integers and values may be up to 16,383 bytes long.
It is intended to be used to store configuration-related information,
like network settings, radio channels, etc.

 * Robust data format which requires no initialization.
 * Supports multiple values with the same key.
 * Data can be appended without erasing EEPROM.
 * Max size of settings data can be easily increased in the future,
   as long as it doesn't overlap with application data.

The format was inspired by the [OLPC manufacturing data format][].

Since the beginning of EEPROM often contains application-specific
information, the best place to store settings is at the end of EEPROM
(the "top"). Because we are starting at the end of EEPROM, it makes
sense to grow the list of key-value pairs downward, toward the start of
EEPROM.

Each key-value pair is stored in memory in the following format:

Order    | Size     | Name         | Description
--------:|---------:|--------------|-------------------------------
       0 |        2 | `key`        | 16-bit key
      -2 |        1 | `size_check` | One's-complement of next byte
      -3 |   1 or 2 | `size`       | The size of `value`, in bytes
-4 or -5 | variable | `value`      | Value associated with `key`

The end of the key-value pairs is denoted by the first invalid entry.
An invalid entry has any of the following attributes:

 * The `size_check` byte doesn't match the one's compliment of the
   `size` byte (or `size_low` byte).
 * The key has a value of 0x0000.

[OLPC manufacturing data format]: http://wiki.laptop.org/go/Manufacturing_data
core/lib/settings: Added `SETTINGS_CONF_SKIP_CONVENIENCE_FUNCS`.

Unfortunately, some platforms don't properly drop unreferenced functions,
so on these broken platforms we can save a significant amount
of space by skipping the definition of the convenience functions.
Fix #183 (short term fix)

This is a temporary fix for #183, so that things can
build cleanly until the issue is fixed properly.

If RIMESTATS_CONF_ENABLED is 0, rimestats.foo will always
read as 0, since RIMESTATS_ADD(foo) doesn't do anything
Provide a macro to read rimestats when enabled
Rename RIMESTATS_CONF_ON to RIMESTATS_CONF_ENABLED
Replace reads of rimestats with RIMESTATS_GET(x)
Fix a mismatch between declaration and definition
ctk-curses: Introduce CURSES_LIB makefile variable

This should allow overriding it depending on $(HOST_OS).
ctk-curses: Remove extra mouse events pumping loop

It was added to avoid getting garbage keyboard input in some cases,
however it seems not to happen very often and might be the cause
of hang in OSX. If garbage input happens again we can always try
to pump a single event each time instead of looping anyway.
ctk-curses: Guard ncurses-specific mouse function calls

The mouse support is ncurses-specific so guard it with proper #ifdef.
ctk-curses: add CURSES_LIB to TARGET_LIBFILES, not LDFLAGS

It seems TARGET_LIBFILES is used at the end of the link command,
unlike LDFLAGS, which should help when only a static curses lib is
available, like on Haiku.
ctk-curses: C89

At least Haiku still uses gcc2 by default.
ctk-curses: Introduce CTK-specific color names

Since ncurses also defines COLOR_BLACK and friends, and we want
to avoid including curses.h in contiki-conf.h, define CTK_COLOR_*
constants and map them to curses colors in ctk-curses.c.