vim-patch:8.1.0588: cannot define a sign with space in the text

Problem:    Cannot define a sign with space in the text.
Solution:   Allow for escaping characters. (Ben Jackson, closes vim/vim#2967)
06b056e110

src/nvim/ex_cmds.c

@@ -5685,6 +5685,14 @@ void ex_sign(exarg_T *eap)
             int len;
 
             arg += 5;
+            for (s = arg; s + 1 < p; s++) {
+              if (*s == '\\') {
+                // Remove a backslash, so that it is possible
+                // to use a space.
+                STRMOVE(s, s + 1);
+                p--;
+              }
+            }
 
             // Count cells and check for non-printable chars
             cells = 0;