Add mojo/c/system/{time.h,wait.h}.

time.h contains the types (previously in types.h) and
MojoGetTimeTicks() (previously in functions.h).

wait.h contains MojoWait() and MojoWaitMany() (previously in
functions.h).

handle.h gets MojoClose() (previously in functions.h).

Removal of types.h and functions.h will be done separately.

R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/1783623005 .
diff --git a/mojo/edk/embedder/system_impl_private_entrypoints.cc b/mojo/edk/embedder/system_impl_private_entrypoints.cc
index 3a159ab..2e6d380 100644
--- a/mojo/edk/embedder/system_impl_private_entrypoints.cc
+++ b/mojo/edk/embedder/system_impl_private_entrypoints.cc
@@ -9,8 +9,11 @@
 #include "mojo/edk/util/ref_ptr.h"
 #include "mojo/public/c/system/buffer.h"
 #include "mojo/public/c/system/data_pipe.h"
-#include "mojo/public/c/system/functions.h"
+#include "mojo/public/c/system/handle.h"
 #include "mojo/public/c/system/message_pipe.h"
+#include "mojo/public/c/system/result.h"
+#include "mojo/public/c/system/time.h"
+#include "mojo/public/c/system/wait.h"
 #include "mojo/public/platform/native/system_impl_private.h"
 
 using mojo::embedder::internal::g_core;