Issue #12326: sys.platform is now always 'linux2' on Linux

Even if Python is compiled on Linux 3.
diff --git a/configure b/configure
index 508ae34..9d85e35 100755
--- a/configure
+++ b/configure
@@ -2997,6 +2997,7 @@
 	MACHDEP="$ac_md_system$ac_md_release"
 
 	case $MACHDEP in
+	linux*) MACHDEP="linux2";;
 	cygwin*) MACHDEP="cygwin";;
 	darwin*) MACHDEP="darwin";;
         irix646) MACHDEP="irix6";;