patch 9.1.0866: filetype: LLVM IR files are not recognized

Problem:  filetype: LLVM IR files are not recognized
Solution: detect '*.ll' files either as lifelines or llvm filetype
          (Wu, Zhenyu)

closes: #15824

Signed-off-by: Wu, Zhenyu <wuzhenyu@ustc.edu>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index 8a89905..215d750 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -2446,6 +2446,24 @@
   filetype off
 endfunc
 
+func Test_ll_file()
+  filetype on
+
+  " LLVM IR
+  call writefile(['target triple = "nvptx64-nvidia-cuda"'], 'Xfile.ll', 'D')
+  split Xfile.ll
+  call assert_equal('llvm', &filetype)
+  bwipe!
+
+  " lifelines
+  call writefile(['proc main() {}'], 'Xfile.ll', 'D')
+  split Xfile.ll
+  call assert_equal('lifelines', &filetype)
+  bwipe!
+
+  filetype off
+endfunc
+
 func Test_lsl_file()
   filetype on
 
diff --git a/src/version.c b/src/version.c
index 79b3099..7ba9d87 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    866,
+/**/
     865,
 /**/
     864,