patch 8.0.1554: custom plugins loaded with --clean

Problem:    Custom plugins loaded with --clean.
Solution:   Do not include the home directory in 'runtimepath'.
diff --git a/src/proto/option.pro b/src/proto/option.pro
index 59dcd42..60a45e6 100644
--- a/src/proto/option.pro
+++ b/src/proto/option.pro
@@ -1,5 +1,5 @@
 /* option.c */
-void set_init_1(void);
+void set_init_1(int clean_arg);
 void set_string_default(char *name, char_u *val);
 void set_number_default(char *name, long val);
 void free_all_options(void);