patch 9.1.1006: PmenuMatch completion highlight can be combined

Problem:  PmenuMatch completion highlight can be combined
Solution: Combine highlight groups PmenuMatch with Pmenu and
          PmenuMatchSel with PmenuSel (glepnir)

fixes: #15563
closes: #16408

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/dumps/Test_pum_highlights_18.dump b/src/testdir/dumps/Test_pum_highlights_18.dump
new file mode 100644
index 0000000..a57f7a2
--- /dev/null
+++ b/src/testdir/dumps/Test_pum_highlights_18.dump
@@ -0,0 +1,20 @@
+|f+0&#ffffff0|b> @72
+|f+0#40ffff15#e0e0e08|o+0#0000001&@1|B+0#40ffff15&|a+0#0000001&|z| @1|f|o@1|k|i|n|d| | +0#4040ff13#ffffff0@58
+|f+0&#ffd7ff255|o+0#0000001&@1|b+0#4040ff13&|a+0#0000001&|r| @1|f|o@1|k|i|n|d| | +0#4040ff13#ffffff0@58
+|f+0&#ffd7ff255|o+0#0000001&@1|b+0#4040ff13&|a+0#0000001&|l|a| |f|o@1|k|i|n|d| | +0#4040ff13#ffffff0@58
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|-+2#0000000&@1| |O|m|n|i| |c|o|m|p|l|e|t|i|o|n| |(|^|O|^|N|^|P|)| |m+0#00e0003&|a|t|c|h| |1| |o|f| |9| +0#0000000&@34
diff --git a/src/testdir/test_popup.vim b/src/testdir/test_popup.vim
index 0303c42..08b9cd9 100644
--- a/src/testdir/test_popup.vim
+++ b/src/testdir/test_popup.vim
@@ -1511,6 +1511,16 @@
   call term_sendkeys(buf, "\<ESC>S/non_existing_folder\<C-X>\<C-F>")
   call TermWait(buf, 50)
   call VerifyScreenDump(buf, 'Test_pum_highlights_15', {})
+  call term_sendkeys(buf, "\<C-E>\<Esc>")
+
+  call term_sendkeys(buf, ":hi PmenuMatchSel ctermfg=14\<CR>")
+  call TermWait(buf, 50)
+  call term_sendkeys(buf, ":hi PmenuMatch ctermfg=12\<CR>")
+  call term_sendkeys(buf, ":set cot=menu,noinsert,fuzzy\<CR>")
+  call term_sendkeys(buf, "S\<C-X>\<C-O>")
+  call TermWait(buf, 50)
+  call term_sendkeys(buf, "fb")
+  call VerifyScreenDump(buf, 'Test_pum_highlights_18', {})
 
   call term_sendkeys(buf, "\<C-E>\<Esc>")
   call TermWait(buf)