runtime(vim): Update base-syntax, match multiline return types

fixes #14442.
closes: #16914

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

runtime/syntax/testdir/input/vim_ex_def_return_type.vim

@@ -0,0 +1,60 @@
+vim9script
+# Vim9 function return types
+# VIM_TEST_SETUP hi link vimUserType Todo
+
+
+# Issue #14442 (vim.vim: confusion for function return types starting on another line)
+
+def TestA______________________________________________________________():
+    \ void
+enddef
+
+def TestB____(result: dict<list<number>>, fs: list<func(number): number>):
+    \ void
+enddef
+
+def TestC____(maybe: bool, F: func(): dict<func(number): number>): func():
+	\ void
+    return () => {
+    }
+enddef
+
+def TestD____(fs: list<func(): dict<func(number): bool>>): func(): func():
+	\ void
+    return () => () => {
+    }
+enddef
+
+class Tests
+    def TestA__________________________________________________________():
+	\ void
+    enddef
+
+    def TestB(result: dict<list<number>>, fs: list<func(number): number>):
+	\ void
+    enddef
+
+    def TestC(maybe: bool, F: func(): dict<func(number): number>): func():
+	    \ void
+	return () => {
+	}
+    enddef
+
+    def TestD(fs: list<func(): dict<func(number): bool>>): func(): func():
+	    \ void
+	return () => () => {
+	}
+    enddef
+endclass
+
+def F(G: func(number, number, number): lib.Trampoline):
+					\ func(number, number, number):
+					\ func(): lib.Trampoline
+	return ((H: func(number, number, number): lib.Trampoline) =>
+				(a1: number, a2: number, n: number) =>
+				() =>
+		H(a2, (a1 + a2), (n - 1)))(G)
+enddef
+
+defcompile
+