fix some compiler warnings (#39142)

- unused jl_iterate_func
- cast type of realloc in jl_init_threading

(cherry picked from commit 83bee67)

Author: JeffBezanson

src/builtins.c

@@ -504,8 +504,6 @@ STATIC_INLINE void _grow_to(jl_value_t **root, jl_value_t ***oldargs, jl_svec_t
     *n_alloc = newalloc;
 }
 
-static jl_function_t *jl_iterate_func JL_GLOBALLY_ROOTED;
-
 static jl_value_t *do_apply( jl_value_t **args, uint32_t nargs, jl_value_t *iterate)
 {
     jl_function_t *f = args[0];

src/threading.c

@@ -401,8 +401,8 @@ void jl_init_threading(void)
         jl_n_threads = (uint64_t)strtol(cp, NULL, 10);
     if (jl_n_threads <= 0)
         jl_n_threads = 1;
-    jl_measure_compile_time = realloc( jl_measure_compile_time, jl_n_threads * sizeof *jl_measure_compile_time );
-    jl_cumulative_compile_time = realloc( jl_cumulative_compile_time, jl_n_threads * sizeof *jl_cumulative_compile_time );
+    jl_measure_compile_time = (uint8_t*)realloc(jl_measure_compile_time, jl_n_threads * sizeof(*jl_measure_compile_time));
+    jl_cumulative_compile_time = (uint64_t*)realloc(jl_cumulative_compile_time, jl_n_threads * sizeof(*jl_cumulative_compile_time));
 #ifndef __clang_analyzer__
     jl_all_tls_states = (jl_ptls_t*)calloc(jl_n_threads, sizeof(void*));
 #endif