Bug#903068: shapelib FTBFS: update Build-Depends: ruby-ronn -> ronn

[Helmut Grohne]

Source: shapelib
Version: 1.4.1-1
Severity: serious

Since ronn got split out of ruby-ronn, shapelib fails to build from
source. It was not possible to have ruby-ronn temporarily depend on
ronn, because that would have created a dependency cycle. Please update
Build-Depends and replace ruby-ronn with ronn as shapelib uses the
command line tool.

Helmut