Merge pull request #3305 from micromint/critical-cpp

Support building mbed_critical.c with C++ compiler

Author: 0xc0170

platform/mbed_critical.c

@@ -15,6 +15,8 @@
  * limitations under the License.
  */
 
+/* Declare __STDC_LIMIT_MACROS so stdint.h defines UINT32_MAX when using C++ */
+#define __STDC_LIMIT_MACROS
 #include "platform/critical.h"
 
 #include "cmsis.h"