Replace Quoted Strings with Constants where possible
Replace Quoted Strings with Constants where possible

Fixes https://github.com/sass/libsass/issues/1295
Fixes https://github.com/sass/libsass/issues/1328

errorx666/libsass,FishingCactus/libsass,mtwebster/mint-libsass,am11/libsass,saper/libsass,mikebarkas/libsass,saper/libsass,saper/libsass,errorx666/libsass,am11/libsass,technoAri/libsass,saper/libsass,panicinc/libsass,panicinc/libsass,khchanel/libsass,technoAri/libsass,mtwebster/mint-libsass,mikebarkas/libsass,mtwebster/mint-libsass,technoAri/libsass,errorx666/libsass,khchanel/libsass,saper/libsass,errorx666/libsass,am11/libsass,panicinc/libsass,mikebarkas/libsass,FishingCactus/libsass,mikebarkas/libsass,khchanel/libsass,FishingCactus/libsass,panicinc/libsass,mtwebster/mint-libsass,technoAri/libsass,FishingCactus/libsass,panicinc/libsass,mikebarkas/libsass,khchanel/libsass,FishingCactus/libsass,am11/libsass,am11/libsass,khchanel/libsass,mtwebster/mint-libsass,technoAri/libsass