Invoke config.py instead of config.pl

git grep -Fl /config.pl | xargs sed -i -e 's!/config\.pl!/config.py!g'

Also:
* Change one comment in include/mbedtls/check_config.h.
* Change PERL to PYTHON in CMakeLists.txt.
diff --git a/scripts/memory.sh b/scripts/memory.sh
index 3dad289..c415f92 100755
--- a/scripts/memory.sh
+++ b/scripts/memory.sh
@@ -46,10 +46,10 @@
     echo ""
     echo "config-$NAME:"
     cp configs/config-$NAME.h $CONFIG_H
-    scripts/config.pl unset MBEDTLS_SSL_SRV_C
+    scripts/config.py unset MBEDTLS_SSL_SRV_C
 
     for FLAG in $UNSET_LIST; do
-        scripts/config.pl unset $FLAG
+        scripts/config.py unset $FLAG
     done
 
     grep -F SSL_MAX_CONTENT_LEN $CONFIG_H || echo 'SSL_MAX_CONTENT_LEN=16384'