patch 8.2.0665: wrongly assuming Python executable is called "python"

Problem:    Wrongly assuming Python executable is called "python".
Solution:   Use detected python command. (Ken Takata, closes #6016)
            Also use CheckFunction if possible.
diff --git a/src/version.c b/src/version.c
index 6f83857..a04f4b3 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    665,
+/**/
     664,
 /**/
     663,