Add documentation to 'file' AnsibleModule definition for internals.

The parameters 'diff_peek' and 'validate' are not expected to be used
by users. They are internal. To make it clear, this change adds the
comments 'Internal use only' to each of those definitions to make
it clear that they are actually used, just not by end-users.

lib/ansible/modules/files/file.py

@@ -87,12 +87,6 @@ options:
       - 'force the creation of the symlinks in two cases: the source file does 
         not exist (but will appear later); the destination exists and is a file (so, we need to unlink the
         "path" file and create symlink to the "src" file in place of it).'
-  diff_peek:
-    required: false
-    description:
-      - "Only check whether the file looks like binary. Returns with the parameter
-         'appears_binary' set to True or False depending on the initial content of the
-         file. This option is enabled when the option is set (to any value)."
 '''
 
 EXAMPLES = '''
@@ -161,9 +155,10 @@ def main():
             state = dict(choices=['file','directory','link','hard','touch','absent'], default=None),
             path  = dict(aliases=['dest', 'name'], required=True),
             original_basename = dict(required=False), # Internal use only, for recursive ops
-            recurse  = dict(default='no', type='bool'),
-            force = dict(required=False,default=False,type='bool'),
-            diff_peek = dict(default=None),
+            recurse  = dict(default=False, type='bool'),
+            force = dict(required=False, default=False, type='bool'),
+            diff_peek = dict(default=None), # Internal use only, for internal checks in the action plugins
+            validate = dict(required=False, default=None), # Internal use only, for template and copy
             src = dict(required=False, default=None),
         ),
         add_file_common_args=True,