various spelling fixes

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/952)
diff --git a/ssl/d1_lib.c b/ssl/d1_lib.c
index 6d75225..193f603 100644
--- a/ssl/d1_lib.c
+++ b/ssl/d1_lib.c
@@ -797,7 +797,7 @@
             }
 
             /*
-             * This is unneccessary if rbio and wbio are one and the same - but
+             * This is unnecessary if rbio and wbio are one and the same - but
              * maybe they're not. We ignore errors here - some BIOs do not
              * support this.
              */