x11-toolkits/fltk: the port had been improved (+)

- Add an option to enable limited Cairo rendering support
- Do not strip static libraries upon installation as this
  breaks linking against them (the case for `x11/flruler')
- Restore `files/patch-src_Makefile' which was ditched in
  r447379 (commit 2a288980) in favor of `post-install'
  target because of the above and now this code is mature
  enough and should be less fragile to patch statically
- Garbage-collect no longer useful patch added in r138020
  (commit 2a70195a) back in 2005 which now makes `-lm'
  appear twice in the fltk-config(1)'s LDFLAGS outputs
- Shorten local variable name in the `post-patch' target

Reported by:	pkg-fallout