vim-patch:8.1.1355: obvious mistakes are accepted as valid expressions

Problem:    Obvious mistakes are accepted as valid expressions.
Solution:   Be more strict about parsing numbers. (Yasuhiro Matsumoto,
            closes vim/vim#3981)
16e9b85113

Update vim_str2nr_spec.lua to add more tests that use strict = true.

src/nvim/ops.c

@@ -5017,7 +5017,7 @@ int do_addsub(int op_type, pos_T *pos, int length, linenr_T Prenum1)
                0 + (do_bin ? STR2NR_BIN : 0)
                + (do_oct ? STR2NR_OCT : 0)
                + (do_hex ? STR2NR_HEX : 0),
-               NULL, &n, maxlen);
+               NULL, &n, maxlen, false);
 
     // ignore leading '-' for hex, octal and bin numbers
     if (pre && negative) {