Fix compilation error due to pthread on OS/2

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
(cherry picked from commit b5b1c190)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

bin/vlc.c

@@ -35,13 +35,20 @@
 #include <stdbool.h>
 #include <locale.h>
 #include <signal.h>
-#include <pthread.h>
+#ifdef HAVE_PTHREAD_H
+# include <pthread.h>
+#endif
 #include <unistd.h>
 
 #ifdef __APPLE__
 #include <string.h>
 #endif
 
+#ifdef __OS2__
+# define pthread_t      int
+# define pthread_self() _gettid()
+#endif
+
 
 /* Explicit HACK */
 extern void LocaleFree (const char *);