Round the number of pages passed to Memory.grow. NFC

Without this the trace line below prints (somewhat confusingly):

```
growMemory: 80740352 (+1048576 bytes / 16.999984741210938 pages)
```

Author: sbc100

src/library.js

@@ -190,7 +190,7 @@ addToLibrary({
   // it. Returns 1 on success, 0 on error.
   $growMemory: (size) => {
     var b = wasmMemory.buffer;
-    var pages = (size - b.byteLength + {{{ WASM_PAGE_SIZE - 1 }}}) / {{{ WASM_PAGE_SIZE }}};
+    var pages = ((size - b.byteLength + {{{ WASM_PAGE_SIZE - 1 }}}) / {{{ WASM_PAGE_SIZE }}}) | 0;
 #if RUNTIME_DEBUG
     dbg(`growMemory: ${size} (+${size - b.byteLength} bytes / ${pages} pages)`);
 #endif

test/other/metadce/test_metadce_mem_O3_grow.gzsize

@@ -1 +1 @@
-2570
+2571

test/other/metadce/test_metadce_mem_O3_grow.jssize

@@ -1 +1 @@
-5344
+5346