[arch-dev-public] Freetype 2.5.1 in [testing]

This release has changed the location of most header files. Theoretically nothing should change, since build systems are supposed to get the includedir via freetype-config or pkg-config, while sources are supposed to first #include and then include other files via macros, e.g. #include FT_FREETYPE_H. But as we all know the situation de facto is often different, so I'm giving you a chance to test and comment before moving freetype2 to [extra]. I'll also be making build tests with some randomly chosen packages which depend on it. Would be nice if I could get signoffs, even though Freetype isn't destined for [core].