Switch GCC url tail .bz2 ==> .gz

 - More portable (Gzip more common than bzip2)
 - No .bz2 files are present for 6.4 on GNU FTP server
 - Fixes #408

Author: zbeekman

prerequisites/build-functions/set_or_print_url.sh

@@ -52,7 +52,7 @@ set_or_print_url()
         gcc_tail="branches/${version_to_build}"
       fi
     else
-      gcc_tail="gcc-${version_to_build}.tar.bz2"
+      gcc_tail="gcc-${version_to_build}.tar.gz"
     fi
   fi
   package_url_tail=(

prerequisites/install-functions/download-all-prerequisites.sh

@@ -16,7 +16,7 @@ function download_all_prerequisites()
     ./install.sh --package gcc  --only-download
     gcc_version=$(./install.sh -V gcc)
     cd prerequisites/downloads/
-    tar xf gcc-${gcc_version}.tar.bz2 || emergency "tar didn't work"
+    tar xf gcc-${gcc_version}.tar.[bg]z* || emergency "tar didn't work"
     listing=$(ls -lt)
     cd gcc-${gcc_version}
   fi