Improved build system and POSIX compatibility

Fixed few bugs related to build system and POSIX compatabilty.

src/IO.c

@@ -1,5 +1,5 @@
 #include <BH/IO.h>
-#include <malloc.h>
+#include <stdlib.h>
 
 
 #define BUFFER_SIZE (sizeof(char *))

src/Platform/Dummy/Tss.c

@@ -3,13 +3,14 @@
 
 int BH_TssCreate(BH_GenericCallback callback)
 {
-
     BH_UNUSED(callback);
+    return 0;
 }
 
 
 void *BH_TssRead(int index)
 {
+    BH_UNUSED(index);
     return NULL;
 }