Make M-x shell work in emacs.

ports/nacl-spawn/include/spawn.h

 /*
  * Copyright (c) 2014 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include <setjmp.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
@@ skipping 42 matching lines @@
  * Synchronously eval JavaScript.
  *
  * Args:
  *   cmd: Null terminated string containing code to eval.
  *   data: Pointer to a char* to receive eval string result.
  *   len: Pointer to a size_t to receive the length of the result.
  */
 void jseval(const char* cmd, char** data, size_t* len);
 
 /*
+ * Create a pipe that can communicate cross-process via JS.
+ *
+ * Args:
+ *   pipefd: Point to place to store a read [0] and write [1] fd.
+ * Returns:
+ *   Zero on success.
+ * TODO(bradnelson): The should work differently, see both:
+ * https://bugs.chromium.org/p/webports/issues/detail?id=247
+ * https://bugs.chromium.org/p/webports/issues/detail?id=248
+ * Only declared when pipe is not defined as doing -Dpipe=nacl_spawn_pipe
+ * is a common (though not universal) way to inject this.
+ * In this case, system headers declaration of pipe don't always match
+ * this definition of pipe.
+ */
+#if !defined(pipe)
+int nacl_spawn_pipe(int pipefd[2]);
+#endif
+
+/*
+ * Create a pipe that can communicate cross-process via JS w/ flags.
+ *
+ * Args:
+ *   pipefd: Point to place to store a read [0] and write [1] fd.
+ *   flags: Flags to create the fd's with (for example O_NONBLOCK).
+ * Returns:
+ *   Zero on success.
+ * TODO(bradnelson): The should work differently, see both:
+ * https://bugs.chromium.org/p/webports/issues/detail?id=247
+ * https://bugs.chromium.org/p/webports/issues/detail?id=248
+ */
+int nacl_spawn_pipe2(int pipefd[2], int flags);
+
+/*
  * Implement vfork as a macro.
  *
  * Returns:
  *   Pid of a child, or zero if in the child.
  *
  * Done as a macro in order to allow portable implementation of
  * vfork's behavior, which requires multiple returns from the same
  * code location.
  * A before function is called to setup vfork state,
  * followed by setjmp passing its result to an after function.
@@ skipping 26 matching lines @@
  * The newer version of glibc already declared execvpe
  */
 #if !defined(__GLIBC__) ||  (__GLIBC__ == 2 && __GLIBC_MINOR__ == 9)
 int execvpe(const char *file, char *const argv[], char *const envp[]);
 #endif
 int execlpe(const char *path, const char *arg, ...); /* char* const envp[] */
 
 __END_DECLS
 
 #endif /* NACL_SPAWN_SPAWN_H_ */