patch 8.1.1550: when a popup has left padding text may be cut off

Problem:    When a popup has left padding text may be cut off.
Solution:   Add the border and padding when computing the size.
diff --git a/src/testdir/dumps/Test_popupwin_21.dump b/src/testdir/dumps/Test_popupwin_21.dump
index 836abe4..4a32eaa 100644
--- a/src/testdir/dumps/Test_popupwin_21.dump
+++ b/src/testdir/dumps/Test_popupwin_21.dump
@@ -5,11 +5,11 @@
 |5| @40|║+0#0000001#ffd7ff255| @11|║| +0#0000000#ffffff0@18
 |6| |╔+0#0000001#ffd7ff255|═@8| +0#0000000#ffffff0@9| +0#0000001#ffd7ff255@14| +0#0000000#ffffff0@4|╚+0#0000001#ffd7ff255|═@11|╝| +0#0000000#ffffff0@18
 |7| |║+0#0000001#ffd7ff255|b|o|r|d|e|r| |T|L| +0#0000000#ffffff0@9| +0#0000001#ffd7ff255@3|p|a|d@1|i|n|g|s| @2| +0#0000000#ffffff0@37
-|8| @20| +0#0000001#ffd7ff255@14| +0#0000000#ffffff0@37
-|9| @20| +0#0000001#ffd7ff255@14| +0#0000000#ffffff0@37
-|1|0| @72
-|1@1| @72
-|1|2| @72
+|8| @20| +0#0000001#ffd7ff255@14| +0#0000000#ffffff0@16|║+0#0000001#ffd7ff255| @2|w|r|a|p@1|e|d| |l|o|n|g|e|r| |t|e
+|9+0#0000000#ffffff0| @20| +0#0000001#ffd7ff255@14| +0#0000000#ffffff0@16|║+0#0000001#ffd7ff255| @2|x|t| @14
+|1+0#0000000#ffffff0|0| @72
+|1@1| @50|║+0#0000001#ffd7ff255| @2|r|i|g|h|t| |a|l|i|g|n|e|d| |t|e|x|t
+|1+0#0000000#ffffff0|2| @72
 |1|3| @72
 |1|4| @72
 @57|1|,|1| @10|T|o|p|