add support for suspending/resuming sleep mode in low power apps

some core files have been modified...
trick for fast multihop in RPL

the RPL network will be organized by sequential node ids very fast,
though sometimes it may crush down :(
add app rpl-border-router
add sample 02 - mx web

an simple ipv6-based web server.
add sample 03 - interrupt

describes how to use interrupts in mx2xxcc.
add sample 04 - adc sensors

describes how to read data using ADC sensors
interfaces, e.g. the temperature and light value in mx2xxcc.
add sample 05 - sht11 sensors

describes how to read data using sht11 sensors
interfaces.
add sample 06 - CoAP sample

demonstrates a RESTful server example with CoAP/HTTP,
showing how to develop a server-side application using the REST layer.
add sample 07 - co2 sensor

shows a custom co2 sensor using RS232.