sys: Fix pthread includes to support avr-libs

Missing malloc.h and clock_id_t were causing issues to build.

It was tested with this configuration:

- linux ubuntu 14.04.5
- arduino-mega2560 board
- avr-libc-1.8.0-4.1

This change was needed to build iotivity example

Bug: https://github.com/RIOT-OS/RIOT/issues/6241
Change-Id: I82ce246093b3467dfe9746f999bcc9335dbb65f6
Signed-off-by: Philippe Coval <philippe.coval@osg.samsung.com>

sys/posix/pthread/include/pthread.h

@@ -22,6 +22,10 @@
 
 #include <time.h>
 
+#ifndef __WITH_AVRLIBC__
+#define HAVE_MALLOC_H 1
+#endif
+
 #include "mutex.h"
 #include "sched.h"
 

sys/posix/pthread/include/pthread_cond.h

@@ -25,7 +25,7 @@
 #   include "msp430_types.h"
 #endif
 
-#if defined(__MACH__)
+#if defined(__MACH__) || defined(__WITH_AVRLIBC__)
 typedef int clockid_t;
 #endif
 

sys/posix/pthread/pthread.c

@@ -19,7 +19,6 @@
  * @}
  */
 
-#include <malloc.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <string.h>
@@ -34,6 +33,10 @@
 
 #include "pthread.h"
 
+#ifdef HAVE_MALLOC_H
+#include <malloc.h>
+#endif
+
 #define ENABLE_DEBUG (0)
 
 #if ENABLE_DEBUG

sys/posix/pthread/pthread_tls.c

@@ -16,10 +16,12 @@
  * @}
  */
 
-#include <malloc.h>
-
 #include "pthread.h"
 
+#ifdef HAVE_MALLOC_H
+#include <malloc.h>
+#endif
+
 #define ENABLE_DEBUG (0)
 #include "debug.h"