patch 9.0.1505: error when heredoc content looks like heredoc

Problem:    Error when heredoc content looks like heredoc.
Solution:   Handle curly expressions. (closes #12325)
diff --git a/src/vim.h b/src/vim.h
index 656bcc9..4e0f2cd 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2758,6 +2758,7 @@
 // flags for find_name_end()
 #define FNE_INCL_BR	1	// include [] in name
 #define FNE_CHECK_START	2	// check name starts with valid character
+#define FNE_ALLOW_CURLY	4	// always allow curly braces name
 
 // BSD is supposed to cover FreeBSD and similar systems.
 #if (defined(SUN_SYSTEM) || defined(BSD) || defined(__FreeBSD_kernel__)) \