patch 8.1.0992: a :normal command resets the reg_executing() result

Problem:    A :normal command while executing a register resets the
            reg_executing() result.
Solution:   Save and restore reg_executing. (closes #4066)
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 6e61cca..f30d933 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -10260,6 +10260,7 @@
     sst->save_insertmode = p_im;
     sst->save_finish_op = finish_op;
     sst->save_opcount = opcount;
+    sst->save_reg_executing = reg_executing;
 
     msg_scroll = FALSE;	    /* no msg scrolling in Normal mode */
     restart_edit = 0;	    /* don't go to Insert mode */
@@ -10285,6 +10286,7 @@
     p_im = sst->save_insertmode;
     finish_op = sst->save_finish_op;
     opcount = sst->save_opcount;
+    reg_executing = sst->save_reg_executing;
     msg_didout |= sst->save_msg_didout;	/* don't reset msg_didout now */
 
     /* Restore the state (needed when called from a function executed for