Add diagnostics module in OpenThread (#343)

* Add diagnostics module in OpenThread

  - provide the same diagnostics interface for both CLI and NCP usage
  - implement common diagnostics features based on existing platform interface defined in 'include/platform/'
  - other more platform specific diagnostics features will be processed under platform layer
  - update CLI interface to support diagnostics feature
  - update both Posix and CC2538 platform to support diagnostics feature

* Add diagnostics module unit test

   - move platform.h from "examples/platform" to "include/platform"
   - add test_diag.cpp to test diagnostics module

* Add a configuration option that would enable/disable diagnostics module

Add --enable-diag configuration option to enable/disable diagnostics module when building OpenThread.

src/cli/cli.cpp

@@ -36,7 +36,7 @@
 #include <string.h>
 
 #include <openthread.h>
-#include <openthread-config.h>
+#include <openthread-diag.h>
 
 #include "cli.hpp"
 #include "cli_dataset.hpp"
@@ -86,6 +86,9 @@ const struct Command Interpreter::sCommands[] =
     { "thread", &ProcessThread },
     { "version", &ProcessVersion },
     { "whitelist", &ProcessWhitelist },
+#if OPENTHREAD_ENABLE_DIAG
+    { "diag", &ProcessDiag },
+#endif
 };
 
 otNetifAddress Interpreter::sAddress;
@@ -1477,6 +1480,14 @@ exit:
     AppendResult(error);
 }
 
+#if OPENTHREAD_ENABLE_DIAG
+void Interpreter::ProcessDiag(int argc, char *argv[])
+{
+    // all diagnostics related features are processed within diagnostics module
+    sServer->OutputFormat("%s\r\n", diagProcessCmd(argc, argv));
+}
+#endif
+
 void Interpreter::ProcessLine(char *aBuf, uint16_t aBufLength, Server &aServer)
 {
     char *argv[kMaxArgs];
@@ -1504,6 +1515,11 @@ void Interpreter::ProcessLine(char *aBuf, uint16_t aBufLength, Server &aServer)
 
     cmd = aBuf;
 
+#if OPENTHREAD_ENABLE_DIAG
+    VerifyOrExit((!isDiagEnabled() || (strcmp(cmd, "diag") == 0)),
+                 sServer->OutputFormat("under diagnostics mode, execute 'diag stop' before running any other commands.\r\n"));
+#endif
+
     for (unsigned int i = 0; i < sizeof(sCommands) / sizeof(sCommands[0]); i++)
     {
         if (strcmp(cmd, sCommands[i].mName) == 0)