Style guide tweaks.

I think this is better wording for function documentation. Also note that C++
code uses Google C++ naming rather than OpenSSL, per
c273d2c537dcd4b66e5235dab14cc7d6e983fc09.

Change-Id: I7334296bf1490395b2ba02e8b6ce245635826df2
Reviewed-on: https://boringssl-review.googlesource.com/3500
Reviewed-by: Adam Langley <agl@google.com>

STYLE

diff --git a/STYLE b/STYLE
index 9a1fcd6..cb2d297 100644
--- a/STYLE
+++ b/STYLE
@@ -90,6 +90,10 @@
 
 Naming.
 
+Follow Google naming conventions in C++ files. In C files, use the
+following naming conventions for consistency with existing OpenSSL and C
+styles:
+
 Define structs with typedef named TYPE_NAME. The corresponding struct
 should be named struct type_name_st.
 
@@ -162,8 +166,12 @@
 file. The style is based on that of Go. The first sentence begins with
 the symbol name, optionally prefixed with "A" or "An". Apart from the
 initial mention of symbol, references to other symbols or parameter
-names should be surrounded by |pipes|. Don't be too verbose, but do
-document success and failure behaviors.
+names should be surrounded by |pipes|.
+
+Documentation should be concise but completely describe the exposed
+behavior of the function. Pay special note to success/failure behaviors
+and caller obligations on object lifetimes. If this sacrifices
+conciseness, consider simplifying the function's behavior.
 
 /* EVP_DigestVerifyUpdate appends |len| bytes from |data| to the data which
  * will be verified by |EVP_DigestVerifyFinal|. It returns one on success and