patch 9.1.0568: Cannot expand paths from 'cdpath' setting

Problem:  Cannot expand paths from 'cdpath' setting
          (Daniel Hahler)
Solution: Implement 'cdpath' completion, add the new 'dir_in_path'
          completion type (LemonBoy)

fixes #374
closes: #15205

Signed-off-by: LemonBoy <thatlemon@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/syntax/vim.vim b/runtime/syntax/vim.vim
index 8ea2c1c..b10531e 100644
--- a/runtime/syntax/vim.vim
+++ b/runtime/syntax/vim.vim
@@ -400,7 +400,7 @@
 syn case ignore
 syn keyword	vimUserAttrbKey   contained	bar	ban[g]	cou[nt]	ra[nge] com[plete]	n[args]	re[gister]
 " GEN_SYN_VIM: vimUserAttrbCmplt, START_STR='syn keyword vimUserAttrbCmplt contained', END_STR=''
-syn keyword vimUserAttrbCmplt contained arglist augroup behave buffer color command compiler cscope diff_buffer dir environment event expression file file_in_path filetype function help highlight history keymap locale mapclear mapping menu messages syntax syntime option packadd runtime shellcmd sign tag tag_listfiles user var breakpoint scriptnames
+syn keyword vimUserAttrbCmplt contained arglist augroup behave buffer color command compiler cscope diff_buffer dir environment event expression file file_in_path filetype function help highlight history keymap locale mapclear mapping menu messages syntax syntime option packadd runtime shellcmd sign tag tag_listfiles user var breakpoint scriptnames dir_in_path
 syn keyword	vimUserAttrbCmplt contained	custom customlist nextgroup=vimUserAttrbCmpltFunc,vimUserCmdError
 syn match	vimUserAttrbCmpltFunc contained	",\%([sS]:\|<[sS][iI][dD]>\)\=\%(\h\w*\%([.#]\h\w*\)\+\|\h\w*\)"hs=s+1 nextgroup=vimUserCmdError