Fixes for Moonlight compatibility on the PS Vita. (#110)

* Use pthread for vita thread managment

* Add thread name to pthread and remove ipv6 from vita

* Fix inclusion of pthread.h so that it is only included on specific platforms (__vita__)

* Fix memory release in ThreadProc for psvita platform

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Co-authored-by: MetalfaceScout <logan.mathis@utahtech.edu>
Co-authored-by: Logan Mathis <33127568+MetalfaceScout@users.noreply.github.com>

src/PlatformThreads.h

@@ -12,15 +12,6 @@ typedef struct _PLT_THREAD {
     HANDLE handle;
     bool cancelled;
 } PLT_THREAD;
-#elif defined(__vita__)
-typedef int PLT_MUTEX;
-typedef int PLT_COND;
-typedef struct _PLT_THREAD {
-    int handle;
-    int cancelled;
-    void *context;
-    bool detached;
-} PLT_THREAD;
 #elif defined(__WIIU__)
 typedef OSFastMutex PLT_MUTEX;
 typedef OSFastCondition PLT_COND;