patch 8.2.0512: Vim9: no optional arguments in func type

Problem:    Vim9: no optional arguments in func type.
Solution:   Check for question mark after type.  Find function reference
            without function().
diff --git a/src/vim.h b/src/vim.h
index f986666..535a18d 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1751,6 +1751,7 @@
 # define INIT3(a, b, c)
 # define INIT4(a, b, c, d)
 # define INIT5(a, b, c, d, e)
+# define INIT6(a, b, c, d, e, f)
 #else
 # ifndef INIT
 #  define INIT(x) x
@@ -1758,6 +1759,7 @@
 #  define INIT3(a, b, c) = {a, b, c}
 #  define INIT4(a, b, c, d) = {a, b, c, d}
 #  define INIT5(a, b, c, d, e) = {a, b, c, d, e}
+#  define INIT6(a, b, c, d, e, f) = {a, b, c, d, e, f}
 #  define DO_INIT
 # endif
 #endif