generate include comments

- formalize how aliases and substitutions work together
- add constexpr, #define, typedef support
- check for correct description order
- write short enum, struct members

R=caryclark@google.com

Docs-Preview: https://skia.org/?cl=129455
Bug: skia:6898
Change-Id: Id60fc2ed02f38a7ba4e5cad5ef493d8c674e6183
Reviewed-on: https://skia-review.googlesource.com/129455
Commit-Queue: Cary Clark <caryclark@skia.org>
Reviewed-by: Cary Clark <caryclark@skia.org>
Auto-Submit: Cary Clark <caryclark@skia.org>
diff --git a/docs/SkPixmap_Reference.bmh b/docs/SkPixmap_Reference.bmh
index 03f2b71..432324e 100644
--- a/docs/SkPixmap_Reference.bmh
+++ b/docs/SkPixmap_Reference.bmh
@@ -1,5 +1,5 @@
 #Topic Pixmap
-#Alias Pixmap_Reference
+#Alias Pixmap_Reference ##
 
 #Class SkPixmap