There are more than enough calls doing string manipulations to deserve
its own files, hence do something about it.
This patch also sorts the #include blocks of all files that needed to be
updated, according to the sorting suggestions from CODING_STYLE. Since
pretty much every file needs our string manipulation functions this
effectively means that most files have sorted #include blocks now.
Also touches a few unrelated include files.
These programs should be run manually, typically two instances on a
veth pair to check conflict detection.
Both test programs take the ifname as input, the ACD also takes the
IP address to check, whereas LL (optionally) takes the seed, which
determines the sequence of IP addresses to try.
