Currently we need to build a different binary for each type of copter frame.
This is a preparation for setting all those binaries to a group called
"copter". We create the groups for the rest of the main products for
consistency.
The task generator for the mavlink headers is given a name 'mavlink' and is
added as a dependency to all local static libraries, because all of them use
sources that include mavlink headers. It would be nice to have a good way to
detect sources that use mavlink headers or to declare list of libraries that
use the headers, so that the dependency could be added automatically.
Additionally, there's a minor change in syntax for the task generator: using
strings directly instead of lists.
Gustavo Jose de Sousa
Lucas De Marchi
Andrew Tridgell
Caio Marcelo de Oliveira Filho