Rearrange and fixup abstraction layer

- Replace os_result by dds_retcode_t and move DDS return code defines down.
  Eliminates the need to convert between different return code types.

- Move dds_time_t down and remove os_time.
  Eliminates the need to convert between different time representations and
  reduces code duplication.

- Remove use of Microsoft source-code annotation language (SAL).
  SAL annotations are Microsoft specific and not very well documented. This
  makes it very difficult for contributers to write.

- Rearrange the abstraction layer to be feature-based. The previous layout
  falsely assumed that the operating system dictates which implementation is
  best suited. For general purpose operating systems this is mostly true, but
  embedded targets require a slightly different approach and may not even offer
  all features. The new layout makes it possible to mix-and-match feature
  implementations and allows for features to not be implemented at all.

- Replace the os prefix by ddsrt to avoid name collisions.

- Remove various portions of unused and unwanted code.

- Export thread names on all supported platforms.

- Return native thread identifier on POSIX compatible platforms.

- Add timed wait for condition variables that takes an absolute time.

- Remove system abstraction for errno. The os_getErrno and os_setErrno were
  incorrect. Functions that might fail now simply return a DDS return code
  instead.

- Remove thread-specific memory abstraction. os_threadMemGet and accompanying
  functions were a mess and their use has been eliminated by other changes in
  this commit.

- Replace attribute (re)defines by ddsrt_ prefixed equivalents to avoid name
  collisions and problems with faulty __nonnull__ attributes.

Signed-off-by: Jeroen Koekkoek <jeroen@koekkoek.nl>

src/core/ddsc/tests/entity_status.c

@@ -9,12 +9,14 @@
  *
  * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
  */
+#include <limits.h>
 #include <stdlib.h>
 #include "CUnit/Theory.h"
-#include "ddsc/dds.h"
-#include "os/os.h"
+#include "dds/dds.h"
 #include "RoundTrip.h"
 
+#include "dds/ddsrt/process.h"
+#include "dds/ddsrt/threads.h"
 
 /****************************************************************************
  * Test globals.
@@ -51,9 +53,9 @@ static char*
 create_topic_name(const char *prefix, char *name, size_t size)
 {
     /* Get semi random g_topic name. */
-    os_procId pid = os_getpid();
-    uintmax_t tid = os_threadIdToInteger(os_threadIdSelf());
-    (void) snprintf(name, size, "%s_pid%"PRIprocId"_tid%"PRIuMAX"", prefix, pid, tid);
+    ddsrt_pid_t pid = ddsrt_getpid();
+    ddsrt_tid_t tid = ddsrt_gettid();
+    (void) snprintf(name, size, "%s_pid%"PRIdPID"_tid%"PRIdTID"", prefix, pid, tid);
     return name;
 }