In the 0.5-r2 ebuild, libast is specified as needing =freetype-1* to compile. However, if i remove freetype-1.3.1-r4 and run revdep-rebuild libast compiles fine against freetype-2.1.5-r1. If there is no other reason for having the freetype-1* dependancy I suggest removing it and replacing it with a generic freetype dependancy
made the dependency optional: truetype? ( =media-libs/freetype-1* )