patch 8.1.0515: reloading a script gives errors for existing functions

Problem:    Reloading a script gives errors for existing functions.
Solution:   Allow redefining a function once when reloading a script.
diff --git a/src/main.c b/src/main.c
index d4ff370..d24eafa 100644
--- a/src/main.c
+++ b/src/main.c
@@ -2953,6 +2953,7 @@
     sourcing_name = (char_u *)"command line";
 #ifdef FEAT_EVAL
     current_sctx.sc_sid = SID_CARG;
+    current_sctx.sc_seq = 0;
 #endif
     for (i = 0; i < parmp->n_commands; ++i)
     {
@@ -3183,6 +3184,7 @@
 #ifdef FEAT_EVAL
 	save_current_sctx = current_sctx;
 	current_sctx.sc_sid = SID_ENV;
+	current_sctx.sc_seq = 0;
 	current_sctx.sc_lnum = 0;
 #endif
 	do_cmdline_cmd(initstr);