(telnet_getenv): make somewhat const

git-svn-id: svn://svn.h5l.se/heimdal/trunk/heimdal@9200 ec53bebd-3082-4978-b11e-865c3cabbd6b

appl/telnet/telnetd/authenc.c

@@ -67,9 +67,8 @@ telnet_spin(void)
 }
 
 char *
-telnet_getenv(char *val)
+telnet_getenv(const char *val)
 {
-    extern char *getenv(const char *);
     return(getenv(val));
 }