Blip cleanup

While looking over some details of blip I noticed that it could use a
cleanup pass. Mostly I added comments and reorganized component wiring.
I also deleted unused code and interfaces that were not wired to
anything in tinyos-main.

I did not change any functionality of BLIP.
BLIP no longer starts itself.

The way IPDispatchP was calling its own SplitControl meant that in a top
level app SplitControl.done() would be called twice: once when it was
triggered from IPDispatch and once when the top level app called
SplitControl.start().

Since BLIP provides a SplitControl interface, components that want to
use blip should be able to call start whenever they want and not have
IPDispatch automagically doing it for them.
Improved printf() debugging for blip

I improved the routing table printing to be well formatted.
Reconfigure how DHCP works with blip

While the magical #define to use DHCP or a static IP address with blip
still works, now application writers are encouraged to explicitely
declare by what mechanism they would like their application to aquire
an IPv6 address.

To use a static address based on a #define prefix (IN6_PREFIX) add:

    components StaticIPAddressC;

to your application. To use DHCP, add:

    components Dhcp6C;

to your application.

I changed the name from NoDhcpC to StaticIpAddressC because I hope to
implement SLAAC, and in that case there are two alternatives to a static
IP, and a more descriptive name is needed.
Improved pack_address() to better use hdr comp.

RFC6282 allows a node to completely elide the src address of the ipv6
header if the prefix matches the global prefix and the lower 64 bits can
be determined from other parts of the packet. This patch adds that
support by checking to see if the EUI64 that is sent in the 15.4 header
matches the lower 64 bits of the address to be packed.
BLIP: Added UDP checksum recalculation

In the case that a transmitting node sends a UDP packet and uses
stateful address compression, the UDP checksum it calculates is "wrong".
That is, it calculates it when it doesn't know its full address.
Therefore, when its address gets expanded and the UDP packet makes it to
the end host, the checksum is invalid.

This patch checks for when stateful address uncompression is used and
rechecks the checksum in that case.

This patch could be expanded to handle more headers and other checksums,
as well as a check to verify the old checksum is still correct before
creating a new one (on incorrect data at that point).
Fixed subtle bug in inet_ntop6

The formatting for certain ipv6 address was wrong.
Check buffer lengths before reading memory

The lib6lowpan code was assuming it had a well formed incoming packet.
It returned errors if it got unexpected bits, but never if it didn't get
enough bits, even though the valid length of the buffer was passed to
the unpack function. This would occasionally cause errors much later
because invalid packets were being processed and the length was invalid.

This commit adds length checking throughout the entire unpack stack to
make sure that the incoming packet is long enough for each part being
unpacked.
Updated lib6lowpan tests

The tests now work with the changed lib6lowpan code.
Fixed warnings

I fixed a couple little nits that caused compiler warnings.
Fix issue with length byte in extension headers

6lowpan compression specifies that the length byte of a compressed
extension header is the number of bytes that follow the length byte.
Therefore it should not include the header type nor the length byte in
the total.

This commit fixes that and reworks how the extension header compression
functions work so that keeping track of buffers isn't spread to multiple
functions. Also, I fixed one of the tests so that it now compressess,
uncompresses, and recompresses a series of headers to verify that it is
working.