Remove long_u: hashtab: Refactor long_u type.

hashtab.h:
- hash_T: long_u -> size_t.

  In principle, a hash value could thought of as just an unsigned number
  without size semantics (uint32_t or uint64_t).  But it is used as
  index at some places, and so, size_t is also eligible. Therea re some
  places where assignments occur between hash_T and size_t variables, in
  both directions. Therefore, if we define hash_T to be of a type having
  a different width than that of size_t, we will have an incorrect
  assignment somewhere that will require an assert/guard.  So the most
  sensible option here seems to do hast_T to be size_t too.

- hashtab_T.ht_mask: long_u -> hash_T.

  Masks are used to be combined with hash_T values, so they should be of
  the same type.

hashtab.c:
- hash_may_resize(): oldsize: long_u -> size_t.
- hash_may_resize(): newsize: long_u -> size_t.
- hash_may_resize(): newmask: long_u -> hash_T.

src/nvim/hashtab.c

@@ -281,7 +281,7 @@ static int hash_may_resize(hashtab_T *ht, size_t minitems)
     // removed items, so that they get cleaned up).
     // Shrink the array when it's less than 1/5 full. When growing it is
     // at least 1/4 full (avoids repeated grow-shrink operations)
-    long_u oldsize = ht->ht_mask + 1;
+    size_t oldsize = ht->ht_mask + 1;
     if ((ht->ht_filled * 3 < oldsize * 2) && (ht->ht_used > oldsize / 5)) {
       return OK;
     }
@@ -303,7 +303,7 @@ static int hash_may_resize(hashtab_T *ht, size_t minitems)
     minsize = minitems * 3 / 2;
   }
 
-  long_u newsize = HT_INIT_SIZE;
+  size_t newsize = HT_INIT_SIZE;
   while (newsize < minsize) {
     // make sure it's always a power of 2
     newsize <<= 1;
@@ -327,12 +327,12 @@ static int hash_may_resize(hashtab_T *ht, size_t minitems)
     ? ht->ht_smallarray
     : xmalloc(sizeof(hashitem_T) * newsize);
 
-  memset(newarray, 0, (size_t)(sizeof(hashitem_T) * newsize));
+  memset(newarray, 0, sizeof(hashitem_T) * newsize);
 
   // Move all the items from the old array to the new one, placing them in
   // the right spot. The new array won't have any removed items, thus this
   // is also a cleanup action.
-  long_u newmask = newsize - 1;
+  hash_T newmask = newsize - 1;
   int todo = (int)ht->ht_used;
 
   for (hashitem_T *olditem = oldarray; todo > 0; ++olditem) {

src/nvim/hashtab.h

@@ -4,7 +4,7 @@
 #include "nvim/vim.h"
 
 /// Type for hash number (hash calculation result).
-typedef long_u hash_T;          
+typedef size_t hash_T;          
 
 /// The address of "hash_removed" is used as a magic number
 /// for hi_key to indicate a removed item. 
@@ -53,10 +53,10 @@ typedef struct hashitem_S {
 ///
 /// The hashtable grows to accommodate more entries when needed.
 typedef struct hashtable_S {
-  long_u ht_mask;               /// mask used for hash value
+  hash_T ht_mask;               /// mask used for hash value
                                 /// (nr of items in array is "ht_mask" + 1)
-  long_u ht_used;               /// number of items used
-  long_u ht_filled;             /// number of items used or removed
+  size_t ht_used;               /// number of items used
+  size_t ht_filled;             /// number of items used or removed
   int ht_locked;                /// counter for hash_lock()
   int ht_error;                 /// when set growing failed, can't add more
                                 /// items before growing works