patch 8.0.1841: HP-UX does not have setenv()

Problem:    HP-UX does not have setenv().
Solution:   Use vim_setenv(). (John Marriott)

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1841,
 /**/
     1840,
 /**/