patch 8.2.4930: interpolated string expression requires escaping

Problem:    Interpolated string expression requires escaping.
Solution:   Do not require escaping in the expression.
diff --git a/src/proto/typval.pro b/src/proto/typval.pro
index 5b1f974..6a8d0ac 100644
--- a/src/proto/typval.pro
+++ b/src/proto/typval.pro
@@ -68,11 +68,11 @@
 int tv_equal(typval_T *tv1, typval_T *tv2, int ic, int recursive);
 int eval_option(char_u **arg, typval_T *rettv, int evaluate);
 int eval_number(char_u **arg, typval_T *rettv, int evaluate, int want_string);
-int eval_string(char_u **arg, typval_T *rettv, int evaluate);
-int eval_lit_string(char_u **arg, typval_T *rettv, int evaluate);
+int eval_string(char_u **arg, typval_T *rettv, int evaluate, int interpolate);
+int eval_lit_string(char_u **arg, typval_T *rettv, int evaluate, int interpolate);
+int eval_interp_string(char_u **arg, typval_T *rettv, int evaluate);
 char_u *tv2string(typval_T *tv, char_u **tofree, char_u *numbuf, int copyID);
 int eval_env_var(char_u **arg, typval_T *rettv, int evaluate);
-int eval_interp_string(char_u **arg, typval_T *rettv, int evaluate);
 linenr_T tv_get_lnum(typval_T *argvars);
 linenr_T tv_get_lnum_buf(typval_T *argvars, buf_T *buf);
 buf_T *tv_get_buf(typval_T *tv, int curtab_only);