New support for fixed size fields in ROS Messages

The 2.5.0 Toolchain supports fixed size fields in ROS Messages, in
scripting/taskbrowser. Since a fixed size field is a different type than a
variable size field, we had to come up with a new type name.For each ROS
message 'Message' in 'package' we have now:

package.Message // normal variable (struct)
package.Message[] // sequence, variable sized
package.cMessage[] // fixed size sequence, the new one.

An alternative name could have been package.Message[N], but the filling in
of 'N' would have to be left to the displaying program, or the parser...

I would prefer usage/display patterns showing the size between [...], but
even then, the type must have a name, from which we can deduce its fixed
size, or the type info objects tells us it is (and provides us the name to

Anyway, I expect as usual some discussion and the 'c' variant is probably
going to change to something else...