Reduce variable scope.

This resolves #274.

src/chunk_mmap.c

@@ -6,14 +6,16 @@
 static void *
 chunk_alloc_mmap_slow(size_t size, size_t alignment, bool *zero, bool *commit)
 {
-	void *ret, *pages;
-	size_t alloc_size, leadsize;
+	void *ret;
+	size_t alloc_size;
 
 	alloc_size = size + alignment - PAGE;
 	/* Beware size_t wrap-around. */
 	if (alloc_size < size)
 		return (NULL);
 	do {
+		void *pages;
+		size_t leadsize;
 		pages = pages_map(NULL, alloc_size);
 		if (pages == NULL)
 			return (NULL);