avoid explicit casts if possible (small refacotring on dict.c, system.c)

dict.c

@@ -12,11 +12,13 @@ xh_value_hash(const void *key, void *data)
 {
   union { double f; int i; } u;
   pic_value val = *(pic_value *)key;
-  int hash;
+  int hash, vtype;
 
   UNUSED(data);
 
-  switch (pic_vtype(val)) {
+  vtype = pic_vtype(val);
+
+  switch (vtype) {
   default:
     hash = 0;
     break;
@@ -31,11 +33,11 @@ xh_value_hash(const void *key, void *data)
     hash = pic_int(val);
     break;
   case PIC_VTYPE_HEAP:
-    hash = (int)pic_ptr(val);
+    hash = (int)(intptr_t)pic_ptr(val);
     break;
   }
 
-  return hash + (int)pic_vtype(val);
+  return hash + vtype;
 }
 
 static int

system.c

@@ -105,12 +105,12 @@ pic_system_getenvs(pic_state *pic)
 
   for (envp = pic->envp; *envp; ++envp) {
     pic_str *key, *val;
-    int i;
+    size_t i;
 
     for (i = 0; (*envp)[i] != '='; ++i)
       ;
 
-    key = pic_make_str(pic, *envp, (size_t)i);
+    key = pic_make_str(pic, *envp, i);
     val = pic_make_str_cstr(pic, getenv(pic_str_cstr(key)));
 
     /* push */