LibC: Make _get_uthread a macro

This allows nice inlining :)

userspace/libraries/LibC/errno.cpp

@@ -1,8 +1,6 @@
 #include <errno.h>
 #include <pthread.h>
 
-extern uthread* _get_uthread();
-
 int* __errno_location()
 {
 	return &_get_uthread()->errno_;

userspace/libraries/LibC/include/pthread.h

@@ -87,6 +87,20 @@ struct uthread
 #define _PTHREAD_ATFORK_CHILD   2
 void _pthread_call_atfork(int state);
 
+#if defined(__x86_64__)
+#define _get_uthread() ({ \
+		struct uthread* __tmp; \
+		asm volatile("movq %%fs:0, %0" : "=r"(__tmp)); \
+		__tmp; \
+	})
+#elif defined(__i686__)
+#define _get_uthread() ({ \
+		struct uthread* __tmp; \
+		asm volatile("movl %%gs:0, %0" : "=r"(__tmp)); \
+		__tmp; \
+	})
+#endif
+
 int			pthread_atfork(void (*prepare)(void), void (*parent)(void), void(*child)(void));
 int			pthread_attr_destroy(pthread_attr_t* attr);
 int			pthread_attr_getdetachstate(const pthread_attr_t* attr, int* detachstate);

userspace/libraries/LibC/pthread.cpp

@@ -54,17 +54,6 @@ extern "C" void _pthread_trampoline_cpp(void* arg)
 	ASSERT_NOT_REACHED();
 }
 
-uthread* _get_uthread()
-{
-	uthread* result;
-#if ARCH(x86_64)
-	asm volatile("movq %%fs:0, %0" : "=r"(result));
-#elif ARCH(i686)
-	asm volatile("movl %%gs:0, %0" : "=r"(result));
-#endif
-	return result;
-}
-
 static void free_uthread(uthread* uthread)
 {
 	if (uthread->dtv[0] == 0)