patch 8.0.1663: cannot build without multi-byte feature

Problem:    Cannot build without multi-byte feature.
Solution:   Add #ifdef.

Author: brammool

src/ex_docmd.c

@@ -5308,6 +5308,7 @@ skip_cmd_arg(
     return p;
 }
 
+#if defined(FEAT_MBYTE) || defined(PROTO)
     int
 get_bad_opt(char_u *p, exarg_T *eap)
 {
@@ -5319,6 +5320,7 @@ get_bad_opt(char_u *p, exarg_T *eap)
 	eap->bad_char = *p;
     return FAIL;
 }
+#endif
 
 /*
  * Get "++opt=arg" argument.

src/version.c

@@ -762,6 +762,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1663,
 /**/
     1662,
 /**/