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>

include/openssl/rc4.h

diff --git a/include/openssl/rc4.h b/include/openssl/rc4.h
index 4c13117..727b474 100644
--- a/include/openssl/rc4.h
+++ b/include/openssl/rc4.h
@@ -64,6 +64,9 @@
 #endif
 
 
+/* RC4. */
+
+
 typedef struct rc4_key_st {
   uint32_t x, y;
   /* data is sometimes used as an array of 32-bit values and sometimes as 8-bit