Explain that the source code was generated by this script

Author: kud1ing

src/etc/unicode.py

@@ -235,6 +235,10 @@ def emit_decomp_module(f, canon, compat):
 rf = open(r, "w")
 
 (canon_decomp, compat_decomp, gencats) = load_unicode_data("UnicodeData.txt")
+
+# Explain that the source code was generated by this script.
+rf.write('// The following code was generated by "src/etc/unicode.py"\n\n')
+
 emit_property_module(rf, "general_category", gencats)
 
 #emit_decomp_module(rf, canon_decomp, compat_decomp)