Added dual license option, proper copyright

Fixed #115

LICENSE-APACHE

@@ -178,7 +178,7 @@
    APPENDIX: How to apply the Apache License to your work.
 
       To apply the Apache License to your work, attach the following
-      boilerplate notice, with the fields enclosed by brackets "{}"
+      boilerplate notice, with the fields enclosed by brackets "[]"
       replaced with your own identifying information. (Don't include
       the brackets!)  The text should be enclosed in the appropriate
       comment syntax for the file format. We also recommend that a
@@ -186,7 +186,7 @@
       same "printed page" as the copyright notice for easier
       identification within third-party archives.
 
-   Copyright 2020 The fast_float authors 
+   Copyright [yyyy] [name of copyright owner]
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.

LICENSE-MIT

@@ -1,3 +1,7 @@
+MIT License
+
+Copyright (c) 2021 The fast_float authors
+
 Permission is hereby granted, free of charge, to any
 person obtaining a copy of this software and associated
 documentation files (the "Software"), to deal in the

script/amalgamate.py

@@ -10,15 +10,25 @@ for filename in ['AUTHORS', 'CONTRIBUTORS']:
         text += '// fast_float by ' + line
       if filename == 'CONTRIBUTORS':
         text += '// with contributions from ' + line
-    processed_files[filename] = text
+    processed_files[filename] = text + '//\n'
 
 # licenses
 for filename in ['LICENSE-MIT', 'LICENSE-APACHE']:
+  lines = []
   with open(filename) as f:
-    text = ''
-    for line in f:
-      text += '// ' + line
-    processed_files[filename] = text
+    lines = f.readlines()
+
+  # Retrieve subset required for inclusion in source
+  if filename == 'LICENSE-APACHE':
+    lines = [
+      '   Copyright 2021 The fast_float authors\n',
+      *lines[189:-1]
+    ]
+
+  text = ''
+  for line in lines:
+    text += '//    ' + line.strip() + '\n'
+  processed_files[filename] = text
 
 # code
 for filename in [ 'fast_float.h', 'float_common.h', 'ascii_number.h', 
@@ -29,20 +39,42 @@ for filename in [ 'fast_float.h', 'float_common.h', 'ascii_number.h',
     for line in f:
       if line.startswith('#include "'): continue
       text += line
-    processed_files[filename] = text
+    processed_files[filename] = '\n' + text
 
 # command line
 import argparse
 
 parser = argparse.ArgumentParser(description='Amalgamate fast_float.')
-parser.add_argument('--license', default='MIT', help='choose license')
+parser.add_argument('--license', default='DUAL', choices=['DUAL', 'MIT', 'APACHE'], help='choose license')
 parser.add_argument('--output', default='', help='output file (stdout if none')
 
 args = parser.parse_args()
 
-text = '\n\n'.join([
+def license_content(license_arg):
+  result = []
+
+  if license_arg == 'DUAL':
+    result += [
+      '// Licensed under the Apache License, Version 2.0, or the\n',
+      '// MIT License at your option. This file may not be copied,\n',
+      '// modified, or distributed except according to those terms.\n',
+      '//\n'
+    ]
+
+  if license_arg in ('DUAL', 'MIT'):
+    result.append('// MIT License Notice\n//\n')
+    result.append(processed_files['LICENSE-MIT'])
+    result.append('//\n')
+  if license_arg in ('DUAL', 'APACHE'):
+    result.append('// Apache License (Version 2.0) Notice\n//\n')
+    result.append(processed_files['LICENSE-APACHE'])
+    result.append('//\n')
+
+  return result
+
+text = ''.join([
   processed_files['AUTHORS'], processed_files['CONTRIBUTORS'], 
-  processed_files['LICENSE-' + args.license],
+  *license_content(args.license),
   processed_files['fast_float.h'], processed_files['float_common.h'], 
   processed_files['ascii_number.h'], processed_files['fast_table.h'],
   processed_files['decimal_to_binary.h'], processed_files['bigint.h'],