patch 8.0.1455: if $SHELL contains a space then 'shell' is incorrect

Problem:    If $SHELL contains a space then the default value of 'shell' is
            incorrect. (Matthew Horan)
Solution:   Escape spaces in $SHELL. (Christian Brabandt, closes #459)

src/version.c

@@ -771,6 +771,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1455,
 /**/
     1454,
 /**/