install newly required header in autotools build system
install newly required header in autotools build system

sass_interface.h #includes sass2scss.h so we need to have the
latter header wherever we have the former one.

am11/libsass,FishingCactus/libsass,am11/libsass,technoAri/libsass,webdev1001/libsass,mtwebster/mint-libsass,TBAPI-0KA/NSass,khchanel/libsass,mikebarkas/libsass,FishingCactus/libsass,mikebarkas/libsass,FishingCactus/libsass,saper/libsass,webdev1001/libsass,mtwebster/mint-libsass,technoAri/libsass,errorx666/libsass,khchanel/libsass,panicinc/libsass,TBAPI-0KA/NSass,TBAPI-0KA/NSass,mtwebster/mint-libsass,saper/libsass,TBAPI-0KA/NSass,technoAri/libsass,webdev1001/libsass,technoAri/libsass,saper/libsass,panicinc/libsass,khchanel/libsass,saper/libsass,technoAri/libsass,mtwebster/mint-libsass,mikebarkas/libsass,khchanel/libsass,saper/libsass,panicinc/libsass,panicinc/libsass,am11/libsass,TBAPI-0KA/NSass,webdev1001/libsass,errorx666/libsass,errorx666/libsass,am11/libsass,mikebarkas/libsass,am11/libsass,panicinc/libsass,errorx666/libsass,mikebarkas/libsass,webdev1001/libsass,khchanel/libsass,FishingCactus/libsass,mtwebster/mint-libsass,TBAPI-0KA/NSass,FishingCactus/libsass