Convert utmp{x}name to int, return useful value. Define _PATH_UTMPX

* syscalls.cc (utmpname): Convert to int.  Return 0 if strdup
	worked, -1 otherwise.
	* include/utmpx.h (_PATH_UTMPX): Define as _PATH_UTMP.
	(utmpxname): Declare as int function.
	* include/sys/utmp.h (utmpname): Ditto.
	* include/cygwin/version.h: Bump API minor version.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/doc/new-features.xml

@@ -52,6 +52,10 @@ Fix (numeric and monetary) decimal point and thousands separator in
 fa_IR and ps_AF locales to be aligned with Linux.
 </para></listitem>
 
+<listitem><para>
+utmpname/utmpxname are now defined as int functions as on Linux.
+</para></listitem>
+
 </itemizedlist>
 
 </sect2>