[kernel] Fix frame allocation for multiple pages

There was an inverted boolean logic in determining how many consecutive
pages were available.

Also adding some memory debugging tools I added to track down the recent
memory bugs:

- A direct debugcon::write call, for logging to the debugcon without the
  possible page faults with the logger.
- A new vm_space::lock call, to make a page not fillable in memory
  debugging mode
- A mode in heap_allocator to always alloc new pages, and lock freed
  pages to cause page faults for use-after-free bugs.
- Logging in kobject on creation and deletion
- Page table cache structs are now page-sized for easy pointer math

src/kernel/debugcon.cpp

@@ -26,6 +26,20 @@ namespace {
     }
 } // anon namespace
 
+void
+write(const char *fmt, ...)
+{
+    char buffer[256];
+
+    va_list va;
+    va_start(va, fmt);
+    size_t n = util::vformat({buffer, sizeof(buffer)}, fmt, va);
+    va_end(va);
+
+    debug_out(buffer, n);
+    debug_out("\r\n", 2);
+}
+
 void
 output(j6_log_entry *entry)
 {