runtime(vim): Update syntax and ftplugin files (#13924)

Improve matching of line-continuations and interspersed comments.

These are now also matched in multiline syntax command patterns,
dictionary literals, and parenthesised expressions and argument lists.

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/syntax/testdir/input/vim_line_continuation.vim

@@ -0,0 +1,49 @@
+" Vim line continuations with interspersed comments
+
+function Foo(
+      "\ param a
+      \ a,
+      "\ param b
+      \ b,
+      "\ param c
+      \ c
+      \)
+  echomsg
+	"\ start string
+	\ $"
+	"\ print a
+	\ a = {a:a},
+	"\ print b
+	\ b = {a:b},
+	"\ print c
+	\ c = {a:c}
+	"\ end string
+	\"
+endfunction
+
+call Foo(
+      "\ arg 1
+      \ 11,
+      "\ arg 2
+      \ 22,
+      "\ arg 3
+      \ 33
+      \)
+
+let dict = #{
+      "\ pair 1
+      \ a: 1,
+      "\ pair 2
+      \ b: 2,
+      "\ pair 3
+      \ c: 3
+      \}
+
+let array = [
+      "\ element 1
+      \ 1,
+      "\ element 2
+      \ 2,
+      "\ element 3
+      \ 3
+      \]

runtime/syntax/testdir/input/vim_syntax.vim

@@ -1,75 +1,164 @@
-" Vim :syntax highlighting
+" Vim :syntax command
+
+syn match testMatch "pattern" contained " tail comment
+" NOTE: comments not currently supported
+syn keyword testKeyword keyword contained " tail comment
+syn region testRegion start="start-pattern" skip="skip-pattern" end="end-pattern" contained " tail comment
+
+" Multiline commands
 
 syn keyword testKeyword
+      "\ OPTIONS
+      "\ conceal option
       \ conceal
+      "\ cchar option
       \ cchar=&
+      "\ contained option
       \ contained
+      "\ containedin option
       \ containedin=testContainer
-      \ nextgroup=testNext,@testCluster
+      "\ nextgroup option
+      \ nextgroup=testNext0,@testCluster
+      "\ transparent option
       \ transparent
+      "\ skipwhite option
       \ skipwhite
+      "\ skipempty option
       \ skipempty
+      "\ skipnl option
       \ skipnl
+      "\ KEYWORDS LIST
+      "\ keyword 1
       \ keyword1
+      "\ keyword 2
       \ keyword2
+      "\ keyword 3
       \ keyword3
 
 syn match testMatch
-      \ "pattern"
+      "\ MATCH PATTERN
+      "\ pattern start
+      \ /
+      "\ part 1 description
+      \pat1a .* pat1b
+      "\ part 2 description
+      \pat2a .* pat2b
+      "\ part 3 description
+      \pat3a .* pat3b
+      "\ pattern end
+      \/
+      "\ OPTIONS
+      "\ conceal option
       \ conceal
+      "\ cchar option
       \ cchar=&
+      "\ contained option
       \ contained
+      "\ containedin option
       \ containedin=testContainer
-      \ nextgroup=testNext,@testCluster
+      "\ nextgroup option
+      \ nextgroup=testNext0,@testCluster
+      "\ transparent option
       \ transparent
+      "\ skipwhite option
       \ skipwhite
+      "\ skipempty option
       \ skipempty
+      "\ skipnl option
       \ skipnl
+      "\ contains option
       \ contains=testContained1,testContained2
+      "\ fold option
       \ fold
+      "\ display option
       \ display
+      "\ extend option
       \ extend
+      "\ excludenl option
       \ excludenl
+      "\ keepend option
       \ keepend
 
 syn region testRegion
+      "\ OPTIONS
+      "\ start option
       \ start="start-pattern"
-      \ end="end-pattern"
+      "\ skip option
       \ skip="skip-pattern"
-      \ contained
+      "\ end option
+      \ end="end-pattern"
+      "\ conceal option
       \ conceal
+      "\ cchar option
       \ cchar=&
+      "\ contained option
       \ contained
+      "\ containedin option
       \ containedin=testContainer
-      \ nextgroup=testNext,@testCluster
+      "\ nextgroup option
+      \ nextgroup=testNext0,@testCluster
+      "\ transparent option
       \ transparent
+      "\ skipwhite option
       \ skipwhite
+      "\ skipempty option
       \ skipempty
+      "\ skipnl option
       \ skipnl
+      "\ contains option
       \ contains=testContained1,testContained2
+      "\ oneline option
       \ oneline
+      "\ fold option
       \ fold
+      "\ display option
       \ display
+      "\ extend option
       \ extend
+      "\ concealends option
       \ concealends
+      "\ excludenl option
       \ excludenl
+      "\ keepend option
       \ keepend
 
 syn cluster testCluster
+      "\ OPTIONS
+      "\ contains option
       \ contains=testContained1,testContained2,testContained3
 
 syn cluster testCluster
+      "\ OPTIONS
+      "\ add option
       \ add=testAdd
+      "\ remove option
       \ remove=testRemove
 
 
-" check multiline group list
+" multiline group list
+
+syn keyword testNext0 keyword
+syn keyword testNext1 keyword
+syn keyword testNext2 keyword
+syn keyword testNext3 keyword
+syn keyword testNext4 keyword
+syn keyword testNext5 keyword
+syn keyword testNext6 keyword
+syn keyword testNext7 keyword
+syn keyword testNext8 keyword
+syn keyword testNext9 keyword
+
 syn keyword testKeyword
+      "\ nextgroup option
       \ nextgroup=
-      \ testNext , 
-      \ testNext2 , 
-      \ @testCluster 
-      \ skipwhite
+      "\ a comment
+      \ testNext0 , testNext1 , 
+      "\ a comment
+      \ testNext[2-8].* , 
+      "\ a comment
+      \ testNext9 , @testCluster skipwhite
+      "\ KEYWORDS LIST
       \ keyword4
       \ keyword5
       \ keyword6
+