runtime(vim): Update base-syntax, improve function definition matching

- Fix highlighting of function names including /fu\%[nction]/ (E.g.,
  s:func(), foo.fu(), fu.func())
- Match :delfunction argument.

Reported by Aliaksei Budavei.

closes: #17428

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

runtime/syntax/testdir/input/vim_ex_function_fold.vim

@@ -66,10 +66,48 @@ function <SID>Foo()
   return 42
 endfunction
 
+function b:dict.Foo()
+  return 42
+endfunction
+
+function w:dict.Foo()
+  return 42
+endfunction
+
+function t:dict.Foo()
+  return 42
+endfunction
+
+function g:dict.Foo()
+  return 42
+endfunction
+
+function s:dict.Foo()
+  return 42
+endfunction
+
+function v:dict.Foo()
+  return 42
+endfunction
+
+function Foo(arg)
+  let l:dict = {}
+  function l:dict.BAR()
+    return 42
+  endfunction
+  function a:arg.BAR()
+    return 42
+  endfunction
+endfunction
+
 function foo#bar#Foo()
   return 42
 endfunction
 
+function g:foo#bar#Foo()
+  return 42
+endfunction
+
 " same name as an Ex command
 function s:ls()
 endfunction
@@ -154,6 +192,14 @@ function Foo(
   return 42
 endfunction
 
+function Foo(
+        x,
+        y,
+        z,
+        ...)
+  return 42
+endfunction
+
 function Foo(x, y = 42, z = "zed")
   return 42
 endfunction
@@ -165,6 +211,13 @@ function Foo(
   return 42
 endfunction
 
+function Foo(
+        x,
+        y = 42,
+        z = "zed")
+  return 42
+endfunction
+
 
 " arguments
 
@@ -179,6 +232,12 @@ function Foo(...)
 endfunction
 
 
+" Issue #16243 (Vim script def parameters syntax highlight is wrong)
+
+function Test(lines = [line('.'), line('.')])
+endfunction
+
+
 " comments
 
 function Foo()
@@ -200,12 +259,12 @@ echo "Foo" | function Foo()
 endfunction
 
 
-" delete function
-
-delfunction Foo
-delfunction foo.bar
-delfunction! Foo
-delfunction foo.bar
+" Issue https://github.com/vim/vim/pull/17420#issuecomment-2927798687
+" (function named /s:fu%\[nction]/)
+
+func! s:func(_, func)
+    return a:func
+endfunc
 
 
 " fold-region ending