patch 8.2.4664: Elvish files are not recognized

Problem:    Elvish files are not recognized.
Solution:   Recognize .elv files. (Bruno Roque, closes #10058)

runtime/filetype.vim

@@ -420,6 +420,9 @@ au BufNewFile,BufRead *.ex call dist#ft#ExCheck()
 au BufRead,BufNewFile mix.lock,*.exs setf elixir
 au BufRead,BufNewFile *.eex,*.leex setf eelixir
 
+" Elvish
+au BufRead,BufNewFile *.elv setf elvish
+
 " Euphoria 3 or 4
 au BufNewFile,BufRead *.eu,*.ew,*.exu,*.exw  call dist#ft#EuphoriaCheck()
 if has("fname_case")

src/testdir/test_filetype.vim

@@ -168,6 +168,7 @@ let s:filename_checks = {
     \ 'eelixir': ['file.eex', 'file.leex'],
     \ 'elm': ['file.elm'],
     \ 'elmfilt': ['filter-rules'],
+    \ 'elvish': ['file.elv'],
     \ 'epuppet': ['file.epp'],
     \ 'erlang': ['file.erl', 'file.hrl', 'file.yaws'],
     \ 'eruby': ['file.erb', 'file.rhtml'],

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4664,
 /**/
     4663,
 /**/