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)
diff --git a/src/version.c b/src/version.c
index a2780f4..86e24fd 100644
--- a/src/version.c
+++ b/src/version.c
@@ -790,6 +790,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    124,
+/**/
     123,
 /**/
     122,