Suppress compiler warnings in dshash.c.

Some compilers complain, not unreasonably, about left-shifting an
int32 "1" and then assigning the result to an int64.  In practice
I sure hope that this data structure never gets large enough that
an overflow would actually occur; but let's cast the constant to
the right type to avoid the hazard.

In passing, fix a typo in dshash.h.

Amit Kapila, adjusted as per comment from Thomas Munro.

Discussion: https://postgr.es/m/CAA4eK1+5vfVMYtjK_NX8O3-42yM3o80qdqWnQzGquPrbq6mb+A@mail.gmail.com

src/backend/lib/dshash.c

@@ -315,7 +315,7 @@ dshash_destroy(dshash_table *hash_table)
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Free all the entries. */
-	size = 1 << hash_table->size_log2;
+	size = ((size_t) 1) << hash_table->size_log2;
 	for (i = 0; i < size; ++i)
 	{
 		dsa_pointer item_pointer = hash_table->buckets[i];
@@ -676,7 +676,7 @@ resize(dshash_table *hash_table, size_t new_size_log2)
 	dsa_pointer new_buckets_shared;
 	dsa_pointer *new_buckets;
 	size_t		size;
-	size_t		new_size = 1 << new_size_log2;
+	size_t		new_size = ((size_t) 1) << new_size_log2;
 	size_t		i;
 
 	/*
@@ -707,10 +707,10 @@ resize(dshash_table *hash_table, size_t new_size_log2)
 	new_buckets = dsa_get_address(hash_table->area, new_buckets_shared);
 
 	/*
-	 * We've allocate the new bucket array; all that remains to do now is to
+	 * We've allocated the new bucket array; all that remains to do now is to
 	 * reinsert all items, which amounts to adjusting all the pointers.
 	 */
-	size = 1 << hash_table->control->size_log2;
+	size = ((size_t) 1) << hash_table->control->size_log2;
 	for (i = 0; i < size; ++i)
 	{
 		dsa_pointer item_pointer = hash_table->buckets[i];

src/include/lib/dshash.h

@@ -39,7 +39,7 @@ typedef dshash_hash (*dshash_hash_function) (const void *v, size_t size,
  * members tranche_id and tranche_name do not need to be initialized when
  * attaching to an existing hash table.
  *
- * Compare and hash functions mus be supplied even when attaching, because we
+ * Compare and hash functions must be supplied even when attaching, because we
  * can't safely share function pointers between backends in general.  Either
  * the arg variants or the non-arg variants should be supplied; the other
  * function pointers should be NULL.  If the arg varants are supplied then the