patch 8.1.1396: 'wincolor' does not apply to lines below the buffer

Problem:    'wincolor' does not apply to lines below the buffer.
Solution:   Also apply 'wincolor' to the "~" lines and the number column.
diff --git a/src/testdir/dumps/Test_wincolor_01.dump b/src/testdir/dumps/Test_wincolor_01.dump
new file mode 100644
index 0000000..0536fd2
--- /dev/null
+++ b/src/testdir/dumps/Test_wincolor_01.dump
@@ -0,0 +1,8 @@
+| +0#af5f00255#ffd7ff255@1|2| | +0#0000001&@4| +0&#e0e0e08| +0&#ffd7ff255@64
+| +0#af5f00255&@1|1| |1+0#0000001&@4|1+0#0000000#e0e0e08@4| | +0#0000001#ffd7ff255@59
+| +0#af5f00255&@1|0| |2+0#0000000#e0e0e08@4>2+0#0000001#ffd7ff255@5| +8&&@59
+| +0#af5f00255&@1|1| |3+0#0000001&| |h|e|r|e+0&#e0e0e08| +0&#ffd7ff255|3| @62
+| +0#af5f00255&@1|2| | +0#0000001&@4| +0&#e0e0e08| +0&#ffd7ff255@64
+|~+0#4040ff13&| @73
+|~| @73
+|-+2#0000000#ffffff0@1| |V|I|S|U|A|L| |-@1| +0&&@34|2| @8|3|,|6| @10|A|l@1| 
diff --git a/src/testdir/test_highlight.vim b/src/testdir/test_highlight.vim
index 7c6cc64..4548457 100644
--- a/src/testdir/test_highlight.vim
+++ b/src/testdir/test_highlight.vim
@@ -573,6 +573,30 @@
   call delete('Xtest_cursorline_with_visualmode')
 endfunc
 
+func Test_wincolor()
+  if !CanRunVimInTerminal()
+    return
+  endif
+
+  call writefile([
+	\ 'set cursorline cursorcolumn rnu',
+	\ 'call setline(1, ["","1111111111","22222222222","3 here 3",""])',
+	\ 'set wincolor=Pmenu',
+	\ '/here',
+	\ ], 'Xtest_wincolor')
+  let buf = RunVimInTerminal('-S Xtest_wincolor', {'rows': 8})
+  call term_wait(buf)
+  call term_sendkeys(buf, "2G5lvj")
+  call term_wait(buf)
+
+  call VerifyScreenDump(buf, 'Test_wincolor_01', {})
+
+  " clean up
+  call term_sendkeys(buf, "\<Esc>")
+  call StopVimInTerminal(buf)
+  call delete('Xtest_wincolor')
+endfunc
+
 " This test must come before the Test_cursorline test, as it appears this
 " defines the Normal highlighting group anyway.
 func Test_1_highlight_Normalgroup_exists()