* cygwinenv.sgml: Add pipe_byte description.

* new-features.sgml (ov-new1.7.15): Add new pipe_byte description for 1.7.15.

winsup/doc/cygwinenv.sgml

@@ -58,6 +58,11 @@ Default is set.</para>
 If supplied, wildcard matching is case insensitive.  The default is <literal>noignorecase</literal></para>
 </listitem>
 
+<listitem>
+<para><envar>(no)pipe_byte</envar> - causes Cygwin to open pipes in byte mode rather than
+message mode.</para>
+</listitem>
+
 <listitem>
 <para><envar>proc_retry:n</envar> - causes <function>fork()</function> and
 <function>exec*()</function> to retry n times when a child process fails