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/SkIPoint_Reference.bmh b/docs/SkIPoint_Reference.bmh
index 61c7394..2ed3b7b 100644
--- a/docs/SkIPoint_Reference.bmh
+++ b/docs/SkIPoint_Reference.bmh
@@ -1,6 +1,6 @@
 #Topic IPoint
-#Alias IPoints
-#Alias IPoint_Reference
+#Alias IPoints ##
+#Alias IPoint_Reference ##
 
 #Struct SkIPoint
 
@@ -454,15 +454,15 @@
 
 #Subtopic IVector
 #Line # alias for IPoint ##
-    #Alias IVector
-    #Alias IVectors
+    #Alias IVector ##
+    #Alias IVectors ##
     #Typedef SkIPoint SkIVector
     #Line # alias for IPoint ##
     #Code
     typedef SkIPoint SkIVector;
     ##
     SkIVector provides an alternative name for SkIPoint. SkIVector and SkIPoint
-    can be used interchangably for all purposes.
+    can be used interchangeably for all purposes.
     #Typedef ##
 ##