Graphs with long edge labels become degenerated

If a derived type has many components of the same type, inheritance graphs becomes degenerated, as edges length depends on length of label. In order to handle this, I added linebreaks. Additionally items from the label list are dropped if there are too many (more than 3 lines of width 40 required).

Here is a contrived example module
```
module test

implicit none
private

type, public :: t0
end type t0

type, extends(t0), public :: t1
end type t1

type, public :: t2
type(t1) :: component_1
type(t1) :: component_2
type(t1) :: component_3
type(t1) :: component_4
type(t1) :: component_5
type(t1) :: component_6
type(t1) :: component_7
type(t1) :: component_8
type(t1) :: component_9
end type t2

type, extends(t2), public :: t3
end type t3

type, extends(t3), public :: t4
end type t4

end module test
```

No source file, test, or entry point is named in the issue. Reproduce the supplied Fortran module and inspect the inheritance-graph generation path to find how long edge labels are laid out and truncated. Done means the graph no longer degenerates while retaining the stated line-break and label-list behavior.

Written by the indexing model from the issue text.