Various documentation fixes.

Add some missing headers and ensure each header has a short description. doc.go
gets confused at declarations that break before the first (, so avoid doing
that. Also skip a/an/deprecated: in markupFirstWord and process pipe words in
the table of contents.

Change-Id: Ia08ec5ae8e496dd617e377e154eeea74f4abf435
Reviewed-on: https://boringssl-review.googlesource.com/2839
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/ec.h b/include/openssl/ec.h
index 7b50caa..86d7de7 100644
--- a/include/openssl/ec.h
+++ b/include/openssl/ec.h
@@ -75,6 +75,9 @@
 #endif
 
 
+/* Low-level operations on elliptic curves. */
+
+
 typedef struct ec_group_st EC_GROUP;
 typedef struct ec_point_st EC_POINT;