[kernel] Add event syscalls

The event object was missing any syscalls. Furthermore, kobject had an
old object_signal implementation (the syscall itself no longer exists),
which was removed. User code should only be able to set signals on
events.

src/kernel/kernel.module

@@ -53,6 +53,7 @@ kernel = module("kernel",
         "syscalls.inc.cog",
         "syscalls/channel.cpp",
         "syscalls/endpoint.cpp",
+        "syscalls/event.cpp",
         "syscalls/handle.cpp",
         "syscalls/object.cpp",
         "syscalls/process.cpp",

src/kernel/syscalls/event.cpp

@@ -0,0 +1,36 @@
+#include <j6/errors.h>
+#include <j6/signals.h>
+
+#include "objects/event.h"
+#include "syscalls/helpers.h"
+
+using namespace obj;
+
+namespace syscalls {
+
+j6_status_t
+event_create(j6_handle_t *self)
+{
+    construct_handle<event>(self);
+    return j6_status_ok;
+}
+
+j6_status_t
+event_signal(event *self, j6_signal_t signals)
+{
+    if (signals & j6_signal_global_mask)
+        return j6_err_invalid_arg;
+
+    self->assert_signal(signals);
+    return j6_status_ok;
+}
+
+j6_status_t
+event_clear(event *self, j6_signal_t mask)
+{
+    self->deassert_signal(~mask);
+    return j6_status_ok;
+}
+
+
+} // namespace syscalls

src/kernel/syscalls/object.cpp

@@ -89,16 +89,6 @@ object_wait_many(j6_handle_t * handles, size_t handles_count, uint64_t mask, j6_
     return j6_status_ok;
 }
 
-j6_status_t
-object_signal(kobject *self, j6_signal_t signals)
-{
-    if ((signals & j6_signal_user_mask) != signals)
-        return j6_err_invalid_arg;
-
-    self->assert_signal(signals);
-    return j6_status_ok;
-}
-
 j6_status_t
 object_close(kobject *self)
 {