Added a shared memory test.

- libposix error printing now configurable via macro definition
- shmget/at/dt tested.

tasks/libposix/include/libposix.h

@@ -0,0 +1,13 @@
+#ifndef __LIBPOSIX_H__
+#define __LIBPOSIX_H__
+
+/* Abort debugging conditions */
+// #define LIBPOSIX_ERROR_MESSAGES
+#if defined (LIBPOSIX_ERROR_MESSAGES)
+#define print_err(...)	printf(__VA_ARGS__)
+#else
+#define print_err(...)
+#endif
+
+
+#endif /* __LIBPOSIX_H__ */