Massive conversion from Package to AutotoolsPackage (#2845)

* Massive conversion from Package to AutotoolsPackage

* Forgot to convert p4est to AutotoolsPackage

* Fix typo

* Fix broken link in docs

var/spack/repos/builtin/packages/gdk-pixbuf/package.py

@@ -25,7 +25,7 @@
 from spack import *
 
 
-class GdkPixbuf(Package):
+class GdkPixbuf(AutotoolsPackage):
     """The Gdk Pixbuf is a toolkit for image loading and pixel buffer
        manipulation. It is used by GTK+ 2 and GTK+ 3 to load and
        manipulate images. In the past it was distributed as part of
@@ -42,8 +42,3 @@ class GdkPixbuf(Package):
     depends_on("jpeg")
     depends_on("libpng")
     depends_on("libtiff")
-
-    def install(self, spec, prefix):
-        configure("--prefix=%s" % prefix)
-        make()
-        make("install")