FLTK-1.3.3 build failure on OSX El Capitan about fltkhs

[deech]

This is a known bug unfortunately. The workaround is to remove FLTK-1.3.3 and do:

brew install --devel fltk

The reason why is explained here: http://hackage.haskell.org/package/fltkhs-0.4.0.5/docs/Graphics-UI-FLTK-LowLevel-FLTKHS.html#g:6

[simonmichael]

After brew remove fltk, I see that brew install fltk (without --devel) does say "This formula either does not compile or function as expected on OS X versions newer than Yosemite due to an upstream incompatibility." I guess there are two pitfalls for El Capitan users here: someone like me whose brew thinks fltk is already installed and up to date (somehow.. prior to OSX upgrade perhaps ?); or, someone who tries brew install fltk, gets the brew warning and doesn't know that --devel is the workaround (because they haven't found your detailed install guide). It's hard to cover everything that could go wrong, I know, but perhaps both of these are worth mentioning somewhere, and the short install guide can more loudly point to the more complete one (or merge with it).