Implement basic support for times().

The kernel now bills processes for time spent in kernelspace and userspace
separately. The accounting is forwarded to the parent process in reap().

This makes the "time" builtin in bash work.

AK/Types.h

@@ -12,7 +12,7 @@ typedef signed int signed_dword;
 typedef signed long long int signed_qword;
 
 typedef decltype(sizeof(void*)) size_t;
-typedef long ssize_t;
+typedef signed_dword ssize_t;
 
 static_assert(sizeof(size_t) == sizeof(dword));
 static_assert(sizeof(ssize_t) == sizeof(signed_dword));