Added an Include library to ACLOCAL_FLAGS to search the autoconf
directory when MacPorts was used to install dependencies.
MacPorts installs by default into /opt/local.
https://github.com/kivy/kivy-ios/issues/19
Default SDL_mixer branch now wants to build version 2, which causes both the SDL_mixer build to fail, and consequently, the kivy build as well.
Xcode Frameworks will show libSDL_mixer.a and libkivy.a are missing.
Specifying the SDL-1.2 branch results in the build working, fixing both problems.
