Fix up several comments and detect problems in the future.

This change fixes up several comments (many of which were spotted by
Kenny Root) and also changes doc.go to detect cases where comments don't
start with the correct word. (This is a common error.)

Since we have docs builders now, these errors will be found
automatically in the future.

Change-Id: I58c6dd4266bf3bd4ec748763c8762b1a67ae5ab3
Reviewed-on: https://boringssl-review.googlesource.com/6440
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/poly1305/poly1305_test.txt b/crypto/poly1305/poly1305_test.txt
index 2a92c12..ad40699 100644
--- a/crypto/poly1305/poly1305_test.txt
+++ b/crypto/poly1305/poly1305_test.txt
@@ -1,4 +1,4 @@
-# RFC 7359, section 2.5.2.
+# RFC 7539, section 2.5.2.
 
 Key = 85d6be7857556d337f4452fe42d506a80103808afb0db2fd4abff6af4149f51b
 Input = "Cryptographic Forum Research Group"