patch 8.1.1687: the evalfunc.c file is too big

Problem:    The evalfunc.c file is too big.
Solution:   Move testing support to a separate file.
diff --git a/src/proto/eval.pro b/src/proto/eval.pro
index 7831eb5..8a19542 100644
--- a/src/proto/eval.pro
+++ b/src/proto/eval.pro
@@ -41,6 +41,7 @@
 int do_unlet(char_u *name, int forceit);
 void del_menutrans_vars(void);
 char_u *get_user_var_name(expand_T *xp, int idx);
+int pattern_match(char_u *pat, char_u *text, int ic);
 int eval0(char_u *arg, typval_T *rettv, char_u **nextcmd, int evaluate);
 int eval1(char_u **arg, typval_T *rettv, int evaluate);
 int get_option_tv(char_u **arg, typval_T *rettv, int evaluate);
@@ -67,6 +68,7 @@
 int eval_isnamec(int c);
 int eval_isnamec1(int c);
 void set_vim_var_nr(int idx, varnumber_T val);
+typval_T *get_vim_var_tv(int idx);
 varnumber_T get_vim_var_nr(int idx);
 char_u *get_vim_var_str(int idx);
 list_T *get_vim_var_list(int idx);
@@ -129,18 +131,7 @@
 int store_session_globals(FILE *fd);
 void last_set_msg(sctx_T script_ctx);
 void reset_v_option_vars(void);
-void prepare_assert_error(garray_T *gap);
 void assert_error(garray_T *gap);
-int assert_equal_common(typval_T *argvars, assert_type_T atype);
-int assert_equalfile(typval_T *argvars);
-int assert_match_common(typval_T *argvars, assert_type_T atype);
-int assert_inrange(typval_T *argvars);
-int assert_bool(typval_T *argvars, int isTrue);
-int assert_report(typval_T *argvars);
-int assert_exception(typval_T *argvars);
-int assert_beeps(typval_T *argvars);
-int assert_fails(typval_T *argvars);
-void fill_assert_error(garray_T *gap, typval_T *opt_msg_tv, char_u *exp_str, typval_T *exp_tv, typval_T *got_tv, assert_type_T atype);
 int typval_compare(typval_T *typ1, typval_T *typ2, exptype_T type, int type_is, int ic);
 char_u *typval_tostring(typval_T *arg);
 int var_exists(char_u *var);