patch 8.2.3893: Vim9: many local variables are initialized with an instruction

Problem:    Vim9: many local variables are initialized with an instruction.
Solution:   Initialize local variables to zero to avoid the instructions.
diff --git a/src/proto/vim9instr.pro b/src/proto/vim9instr.pro
index 4df3af0..0083334 100644
--- a/src/proto/vim9instr.pro
+++ b/src/proto/vim9instr.pro
@@ -65,7 +65,7 @@
 int generate_cmdmods(cctx_T *cctx, cmdmod_T *cmod);
 int generate_undo_cmdmods(cctx_T *cctx);
 int generate_store_var(cctx_T *cctx, assign_dest_T dest, int opt_flags, int vimvaridx, int scriptvar_idx, int scriptvar_sid, type_T *type, char_u *name);
-int generate_store_lhs(cctx_T *cctx, lhs_T *lhs, int instr_count);
+int generate_store_lhs(cctx_T *cctx, lhs_T *lhs, int instr_count, int is_decl);
 void may_generate_prof_end(cctx_T *cctx, int prof_lnum);
 void delete_instr(isn_T *isn);
 void clear_instr_ga(garray_T *gap);