Building Ruby: readline and tk

So I installed libreadline5-dev instead of libreadline6-dev:

$ sudo apt-get remove libreadline6-dev
$ sudo apt-get install libreadline5-dev

Then ext/readline/extconf.rb seems happy:

$ cd ext/readline
$ ruby extconf.rb
checking for tgetnum() in -lncurses... yes
checking for readline/readline.h... yes
checking for readline/history.h... yes
checking for readline() in -lreadline... yes
...

And, for tk support, the simplest way is to download ActiveTcl from http://www.activestate.com/activetcl/downloads and install it. ext/tk/extconf.rb looks for ActiveTcl.