patch 8.2.2384: turtle filetype not recognized

Problem:    Turtle filetype not recognized.
Solution:   Add a rule to detect turtle files. (closes #7722)

runtime/filetype.vim

@@ -1731,8 +1731,13 @@ au BufNewFile,BufRead *.tli			setf tli
 " Telix Salt
 au BufNewFile,BufRead *.slt			setf tsalt
 
-" Tera Term Language
+" Tera Term Language or Turtle
-au BufRead,BufNewFile *.ttl			setf teraterm
+au BufRead,BufNewFile *.ttl
+	\ if getline(1) =~ '^@\?\(prefix\|base\)' |
+	\   setf turtle |
+	\ else |
+	\   setf teraterm |
+	\ endif
 
 " Terminfo
 au BufNewFile,BufRead *.ti			setf terminfo

src/testdir/test_filetype.vim

@@ -733,6 +733,23 @@ func Test_ts_file()
   filetype off
 endfunc
 
+func Test_ttl_file()
+  filetype on
+
+  call writefile(['@base <http://example.org/> .'], 'Xfile.ttl')
+  split Xfile.ttl
+  call assert_equal('turtle', &filetype)
+  bwipe!
+
+  call writefile(['looks like Tera Term Language'], 'Xfile.ttl')
+  split Xfile.ttl
+  call assert_equal('teraterm', &filetype)
+  bwipe!
+
+  call delete('Xfile.ttl')
+  filetype off
+endfunc
+
 func Test_pp_file()
   filetype on
 

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2384,
 /**/
     2383,
 /**/