generate-wire.py: Add scare comments to output.

Discourage developers from modifying files generated by generate-wire.py

tools/generate-wire.py

@@ -472,7 +472,9 @@ for line in fileinput.input(options.files):
             prevfield = parts[2]
         comments=[]
 
-header_template = """#ifndef LIGHTNING_{idem}
+header_template = """/* This file was generated by generate-wire.py */
+/* Do not modify this file! Modify the _csv file it was generated from. */
+#ifndef LIGHTNING_{idem}
 #define LIGHTNING_{idem}
 #include <ccan/tal/tal.h>
 #include <wire/wire.h>
@@ -485,7 +487,9 @@ const char *{enumname}_name(int e);
 #endif /* LIGHTNING_{idem} */
 """
 
-impl_template = """#include <{headerfilename}>
+impl_template = """/* This file was generated by generate-wire.py */
+/* Do not modify this file! Modify the _csv file it was generated from. */
+#include <{headerfilename}>
 #include <ccan/mem/mem.h>
 #include <ccan/tal/str/str.h>
 #include <stdio.h>