Python: follow python guidelines for header usage

Python requires that Python.h is included before any std header.  Not doing so
results in conflicts with standards macros such as `_XOPEN_SOURCE`.  NFC.

llvm-svn: 250673

lldb/scripts/Python/modules/readline/readline.cpp

@@ -1,6 +1,10 @@
-#include <stdio.h>
+// NOTE: Since Python may define some pre-processor definitions which affect the
+// standard headers on some systems, you must include Python.h before any
+// standard headers are included.
 #include "Python.h"
 
+#include <stdio.h>
+
 #ifndef LLDB_DISABLE_LIBEDIT
 #include <editline/readline.h>
 #endif