vim-patch:9.0.0195: metafun files are not recogized (#19746)

Problem:    Metafun files are not recogized.
Solution:   Add filetype detection patterns.
9032b9ceb6

runtime/filetype.vim

@@ -1161,6 +1161,7 @@ au BufNewFile,BufRead *.mf			setf mf
 
 " MetaPost
 au BufNewFile,BufRead *.mp			setf mp
+au BufNewFile,BufRead *.mpxl,*.mpiv,*.mpvi	let b:mp_metafun = 1 | setf mp
 
 " MGL
 au BufNewFile,BufRead *.mgl			setf mgl

runtime/lua/vim/filetype.lua

@@ -668,6 +668,21 @@ local extension = {
   moo = 'moo',
   moon = 'moonscript',
   mp = 'mp',
+  mpiv = function(path, bufnr)
+    return 'mp', function(b)
+      vim.b[b].mp_metafun = 1
+    end
+  end,
+  mpvi = function(path, bufnr)
+    return 'mp', function(b)
+      vim.b[b].mp_metafun = 1
+    end
+  end,
+  mpxl = function(path, bufnr)
+    return 'mp', function(b)
+      vim.b[b].mp_metafun = 1
+    end
+  end,
   mof = 'msidl',
   odl = 'msidl',
   msql = 'msql',

src/nvim/testdir/test_filetype.vim

@@ -360,7 +360,7 @@ let s:filename_checks = {
     \ 'monk': ['file.isc', 'file.monk', 'file.ssc', 'file.tsc'],
     \ 'moo': ['file.moo'],
     \ 'moonscript': ['file.moon'],
-    \ 'mp': ['file.mp'],
+    \ 'mp': ['file.mp', 'file.mpxl', 'file.mpiv', 'file.mpvi'],
     \ 'mplayerconf': ['mplayer.conf', '/.mplayer/config', 'any/.mplayer/config'],
     \ 'mrxvtrc': ['mrxvtrc', '.mrxvtrc'],
     \ 'msidl': ['file.odl', 'file.mof'],