vim-patch:9.1.0796: filetype: libtool files are not recognized

Problem:  filetype: libtool files are not recognized
Solution: detect '*.{lo,la,lai}' as sh filetype
          (Wu, Zhenyu)

closes: vim/vim#15751

bfe568d8c4

Co-authored-by: Wu, Zhenyu <wuzhenyu@ustc.edu>

runtime/lua/vim/filetype.lua

@@ -1068,6 +1068,9 @@ local extension = {
   envrc = detect.sh,
   ksh = detect.ksh,
   sh = detect.sh,
+  lo = 'sh',
+  la = 'sh',
+  lai = 'sh',
   mdd = 'sh',
   sieve = 'sieve',
   siv = 'sieve',

test/old/testdir/test_filetype.vim

@@ -671,7 +671,7 @@ func s:GetFilenameChecks() abort
     \        '/tmp/bash-fc-3Ozjlw', '/tmp/bash-fc.3Ozjlw', 'PKGBUILD', 'APKBUILD', 'file.bash', '/usr/share/doc/bash-completion/filter.sh',
     \        '/etc/udev/cdsymlinks.conf', 'any/etc/udev/cdsymlinks.conf', 'file.bats', '.ash_history', 'any/etc/neofetch/config.conf', '.xprofile',
     \        'user-dirs.defaults', 'user-dirs.dirs', 'makepkg.conf', '.makepkg.conf', 'file.mdd', 'file.cygport', '.env', '.envrc', 'devscripts.conf',
-    \        '.devscripts'],
+    \        '.devscripts', 'file.lo', 'file.la', 'file.lai'],
     \ 'sieve': ['file.siv', 'file.sieve'],
     \ 'sil': ['file.sil'],
     \ 'simula': ['file.sim'],