add declarations for utmpname/utmpxname to appropriate headers

commit 378f8cb5222b63e4f8532c757ce54e4074567e1f added these functions
(as stubs) but left them without declarations. this broke some
autoconf based software that detected linkability of the symbols but
didn't check for a declaration.

include/utmp.h

@@ -22,7 +22,6 @@ struct lastlog {
 #define ut_name ut_user
 #define ut_addr ut_addr_v6[0]
 #define utmp utmpx
-#define utmpname(x) (-1)
 #define e_exit __e_exit
 #define e_termination __e_termination
 
@@ -34,6 +33,7 @@ struct utmp *pututline(const struct utmp *);
 void         setutent(void);
 
 void updwtmp(const char *, const struct utmp *);
+int utmpname(const char *);
 
 int login_tty(int);
 

include/utmpx.h

@@ -43,6 +43,7 @@ void          setutxent(void);
 #define e_exit __e_exit
 #define e_termination __e_termination
 void updwtmpx(const char *, const struct utmpx *);
+int utmpxname(const char *);
 #endif
 
 #define EMPTY           0