Swift: add more doc strings to generated things

misc/codegen/templates/ql_class.mustache

@@ -1,4 +1,11 @@
 // generated by {{generator}}
+/**
+ * This module provides the generated definition of `{{name}}`.
+{{#ql_internal}}
+ * INTERNAL: Do not use.
+{{/ql_internal}}
+ */
+
 private import {{import_prefix}}.Synth
 private import {{import_prefix}}.Raw
 {{#imports}}

misc/codegen/templates/ql_imports.mustache

@@ -1,4 +1,8 @@
 // generated by {{generator}}
+/**
+ * This module exports all modules providing `Element` subclasses.
+ */
+
 {{#imports}}
 import {{.}}
 {{/imports}}

misc/codegen/templates/ql_parent.mustache

@@ -1,4 +1,7 @@
 // generated by {{generator}}
+/**
+ * This module provides the generated parent/child relationship.
+ */
 
 {{#imports}}
 import {{.}}

misc/codegen/templates/ql_stub.mustache

@@ -1,4 +1,10 @@
 // generated by {{generator}}, remove this comment if you wish to edit this file
+/**
+ * This module provides a hand-modifiable wrapper around the generated class `{{name}}`.
+{{#ql_internal}}
+ * INTERNAL: Do not use.
+{{/ql_internal}}
+ */
 private import {{base_import}}
 {{#has_synth_accessors}}
 private import {{import_prefix}}.Raw

misc/codegen/templates/ql_synth_constructor_stub.mustache

@@ -1,4 +1,9 @@
 // generated by {{generator}}, remove this comment if you wish to edit this file
+/**
+ *  This module defines the hook used internally to tweak the characteristic predicate of
+ *  `{{cls.name}}` synthesized instances.
+ *  INTERNAL: Do not use.
+ */
 private import {{import_prefix}}.Raw
 {{#cls}}
 {{#is_db}}
@@ -7,6 +12,10 @@ private import {{import_prefix}}.PureSynthConstructors
 {{/has_subtracted_synth_types}}
 {{/is_db}}
 
+/**
+ *  The characteristic predicate of `{{name}}` synthesized instances.
+ *  INTERNAL: Do not use.
+ */
 predicate construct{{name}}({{#params}}{{^first}}, {{/first}}{{type}} {{param}}{{/params}}) {
   {{#is_db}}
   {{#subtracted_synth_types}}{{^first}} and {{/first}}not construct{{name}}(id){{/subtracted_synth_types}}