Background information: on OSX, the preferred distribution method for libraries is the 'framework' which is a click-and-draggable object that contains headers and libraries together.  The standard location for these is: /Library/Frameworks/

	I have the latest version of officially provided SDL runtime libraries here:

Darlene-Lowes-Mac-mini:/ (222) $ ls /Library/Frameworks/SDL*
/Library/Frameworks/SDL.framework:
Headers   Resources SDL       Versions

/Library/Frameworks/SDL_image.framework:
Frameworks Headers    Resources  SDL_image  Versions

/Library/Frameworks/SDL_mixer.framework:
Frameworks Headers    Resources  SDL_mixer  Versions

	However, automake ignores them, leading to:

checking for sdl-config... no
checking for SDL - version >= 1.1.4... no
*** The sdl-config script installed by SDL could not be found
*** If SDL was installed in PREFIX, make sure PREFIX/bin is in
*** your path, or set the SDL_CONFIG environment variable to the
*** full path to sdl-config.
configure: error: specified client 'sdl' not configurable (SDL >= 1.1.4 is needed (www.libsdl.org))

	The above portion of a log came from a recent attempt to install Freeciv-SDL from source.  I will attach the full copies of configure.ac and Makefile.am that were generated during that attempt, as i don't know enough to be sure what i could trim out without removing useful information.  In any case, the failure is repeatable across a range of versions of OSX with these frameworks.  I did once grab the SDL sources and do the usual configure/make.  The resulting installation does not create a framework, but automake does find the libraries.