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/apidoc_full.sh b/scripts/apidoc_full.sh
index bebab10..dfe1177 100755
--- a/scripts/apidoc_full.sh
+++ b/scripts/apidoc_full.sh
@@ -19,7 +19,7 @@
 CONFIG_BAK=${CONFIG_H}.bak
 cp -p $CONFIG_H $CONFIG_BAK
 
-scripts/config.pl realfull
+scripts/config.py realfull
 make apidoc
 
 mv $CONFIG_BAK $CONFIG_H
diff --git a/scripts/ecc-heap.sh b/scripts/ecc-heap.sh
index 94a04cf..69777a6 100755
--- a/scripts/ecc-heap.sh
+++ b/scripts/ecc-heap.sh
@@ -59,8 +59,8 @@
 
 for F in 0 1; do
     for W in 2 3 4 5 6; do
-        scripts/config.pl set MBEDTLS_ECP_WINDOW_SIZE $W
-        scripts/config.pl set MBEDTLS_ECP_FIXED_POINT_OPTIM $F
+        scripts/config.py set MBEDTLS_ECP_WINDOW_SIZE $W
+        scripts/config.py set MBEDTLS_ECP_FIXED_POINT_OPTIM $F
         make benchmark >/dev/null 2>&1
         echo "fixed point optim = $F, max window size = $W"
         echo "--------------------------------------------"
diff --git a/scripts/footprint.sh b/scripts/footprint.sh
index 697972f..6cabcb9 100755
--- a/scripts/footprint.sh
+++ b/scripts/footprint.sh
@@ -62,9 +62,9 @@
     fi
 
     {
-        scripts/config.pl unset MBEDTLS_TIMING_C || true
-        scripts/config.pl unset MBEDTLS_FS_IO || true
-        scripts/config.pl --force set MBEDTLS_NO_PLATFORM_ENTROPY || true
+        scripts/config.py unset MBEDTLS_TIMING_C || true
+        scripts/config.py unset MBEDTLS_FS_IO || true
+        scripts/config.py --force set MBEDTLS_NO_PLATFORM_ENTROPY || true
     } >/dev/null 2>&1
 
     make clean >/dev/null