patch 8.1.0124: has('vcon') returns true even for non-win32 terminal

Problem:    has('vcon') returns true even for non-win32 terminal.
Solution:   Check the terminal type. (Nobuhiro Takasaki, closes #3106)

src/version.c

@@ -789,6 +789,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    124,
 /**/
     123,
 /**/