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

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

src/misc1.c

@@ -4485,7 +4485,7 @@ vim_unsetenv(char_u *var)
 #ifdef HAVE_UNSETENV
     unsetenv((char *)var);
 #else
-    mch_setenv((char *)var, "", 0);
+    vim_setenv(var, (char_u *)"");
 #endif
 }
 

src/version.c

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