patch 8.0.0743: the 'termsize' option can be set to an invalid value

Problem:    The 'termsize' option can be set to an invalid value.
Solution:   Check the 'termsize' option to be valid.
diff --git a/src/version.c b/src/version.c
index b678ed9..da56b9a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    743,
+/**/
     742,
 /**/
     741,