patch 9.0.0971: escape sequences not recognized without termresponse feature

Problem:    Escape sequences not recognized without the termresponse feature.
Solution:   Recognize escape sequences to avoid display mess up.

src/term.c

@@ -4720,7 +4720,6 @@ modifiers2keycode(int modifiers, int *key, char_u *string)
     return new_slen;
 }
 
-#ifdef FEAT_TERMRESPONSE
 /*
  * Handle a cursor position report.
  */
@@ -5530,7 +5529,6 @@ handle_dcs(char_u *tp, char_u *argp, int len, char_u *key_name, int *slen)
     }
     return OK;
 }
-#endif // FEAT_TERMRESPONSE
 
 /*
  * Check if typebuf.tb_buf[] contains a terminal key code.
@@ -5831,7 +5829,6 @@ check_termcode(
 	    }
 	}
 
-#ifdef FEAT_TERMRESPONSE
 	if (key_name[0] == NUL
 	    // Mouse codes of DEC and pterm start with <ESC>[.  When
 	    // detecting the start of these mouse codes they might as well be
@@ -5903,7 +5900,6 @@ check_termcode(
 		    return -1;
 	    }
 	}
-#endif
 
 	if (key_name[0] == NUL)
 	    continue;	    // No match at this position, try next one

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    971,
 /**/
     970,
 /**/