Support --with-lg-page values larger than system page size.

All mappings continue to be PAGE-aligned, even if the system page size
is smaller.  This change is primarily intended to provide a mechanism
for supporting multiple page sizes with the same binary; smaller page
sizes work better in conjunction with jemalloc's design.

This resolves #467.

test/unit/pack.c

@@ -6,7 +6,7 @@
 #if LG_PAGE <= 14
 #define SZ	(ZU(1) << (LG_PAGE - 2))
 #else
-#define SZ	4096
+#define SZ	ZU(4096)
 #endif
 
 /*

test/unit/pages.c

@@ -7,7 +7,7 @@ TEST_BEGIN(test_pages_huge) {
 
 	alloc_size = HUGEPAGE * 2 - PAGE;
 	commit = true;
-	pages = pages_map(NULL, alloc_size, &commit);
+	pages = pages_map(NULL, alloc_size, PAGE, &commit);
 	assert_ptr_not_null(pages, "Unexpected pages_map() error");
 
 	hugepage = (void *)(ALIGNMENT_CEILING((uintptr_t)pages, HUGEPAGE));