Correct small mistakes in the default Makefile.
Correct small mistakes in the default Makefile.

* A C++ project should use CXX and CXXFLAGS.
* Rules that build actual files should always use the filename as the
  target name.
* Mark some targets as phony.
* Add an all target as default. It's the target name most people use
  since it's the GNU convention.
* Use pattern rules instead of the old style.

am11/libsass,mtwebster/mint-libsass,technoAri/libsass,dahlia/libsass-python,saper/libsass,TBAPI-0KA/NSass,dahlia/libsass-python,admire93/libsass-python,am11/libsass,webdev1001/libsass,khchanel/libsass,FishingCactus/libsass,mtwebster/mint-libsass,rodneyrehm/libsass,mtwebster/mint-libsass,saper/libsass,khchanel/libsass,panicinc/libsass,mtwebster/mint-libsass,technoAri/libsass,am11/libsass,mtwebster/mint-libsass,am11/libsass,moovweb/libsass,mikebarkas/libsass,FishingCactus/libsass,saper/libsass,TBAPI-0KA/NSass,saper/libsass,rodneyrehm/libsass,TBAPI-0KA/NSass,technoAri/libsass,mikebarkas/libsass,khchanel/libsass,FishingCactus/libsass,panicinc/libsass,FishingCactus/libsass,rodneyrehm/libsass,webdev1001/libsass,mikebarkas/libsass,am11/libsass,TBAPI-0KA/NSass,webdev1001/libsass,technoAri/libsass,khchanel/libsass,TBAPI-0KA/NSass,webdev1001/libsass,TBAPI-0KA/NSass,webdev1001/libsass,moovweb/libsass,rodneyrehm/libsass,errorx666/libsass,rodneyrehm/libsass,panicinc/libsass,saper/libsass,mikebarkas/libsass,errorx666/libsass,errorx666/libsass,panicinc/libsass,moovweb/libsass,moovweb/libsass,FishingCactus/libsass,technoAri/libsass,panicinc/libsass,khchanel/libsass,mikebarkas/libsass,admire93/libsass-python,errorx666/libsass