Make the source tree sparse clean.

With this commit, the tree compiles clean with sparse commit 87f4a7fda3d
"Teach 'already_tokenized()' to use the stream name hash table" with patch
"evaluate: Allow sizeof(_Bool) to succeed" available at
http://permalink.gmane.org/gmane.comp.parsers.sparse/2461 applied, as long
as the "include/sparse" directory is included for use by sparse (only),
e.g.:
     make CC="CHECK='sparse -I../include/sparse' cgcc"

include/sparse/sys/wait.h

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2011 Nicira Networks.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __CHECKER__
+#error "Use this header only with sparse.  It is not a correct implementation."
+#endif
+
+#ifndef __SYS_WAIT_SPARSE
+#define __SYS_WAIT_SPARSE 1
+
+#include_next <sys/wait.h>
+
+#undef wait
+#define wait(a) rpl_wait(a)
+pid_t rpl_wait(int *);
+
+#undef waitpid
+#define waitpid(a, b, c) rpl_waitpid(a, b, c)
+pid_t rpl_waitpid(pid_t, int *, int);
+
+#endif /* <sys/wait.h> for sparse */