LibC: Move uthread definition to its own header

Use `__asm__` instead of `asm` to allow compilation with --std=c99 and
before

userspace/libraries/LibC/include/bits/types/uthread.h

@@ -0,0 +1,67 @@
+#ifndef _BITS_TYPES_UTHREAD_H
+#define _BITS_TYPES_UTHREAD_H 1
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#define __need_size_t
+#include <sys/types.h>
+
+#include <bits/types/pthread_t.h>
+#include <stdint.h>
+
+typedef struct _pthread_cleanup_t
+{
+	void (*routine)(void*);
+	void* arg;
+	struct _pthread_cleanup_t* next;
+} _pthread_cleanup_t;
+
+typedef struct _dynamic_tls_entry_t
+{
+	void* master_addr;
+	size_t master_size;
+} _dynamic_tls_entry_t;
+
+typedef struct _dynamic_tls_t
+{
+	int lock;
+	size_t entry_count;
+	_dynamic_tls_entry_t* entries;
+} _dynamic_tls_t;
+
+struct uthread
+{
+	struct uthread* self;
+	void* master_tls_addr;
+	size_t master_tls_size;
+	size_t master_tls_module_count;
+	_dynamic_tls_t* dynamic_tls;
+	_pthread_cleanup_t* cleanup_stack;
+	pthread_t id;
+	int errno_;
+	int cancel_type;
+	int cancel_state;
+	volatile int canceled;
+	// FIXME: make this dynamic
+	uintptr_t dtv[1 + 256];
+};
+
+#if defined(__x86_64__)
+#define _get_uthread() ({ \
+		struct uthread* _uthread; \
+		__asm__ volatile("movq %%fs:0, %0" : "=r"(_uthread)); \
+		_uthread; \
+	})
+#elif defined(__i686__)
+#define _get_uthread() ({ \
+		struct uthread* _uthread; \
+		__asm__ volatile("movl %%gs:0, %0" : "=r"(_uthread)); \
+		_uthread; \
+	})
+#endif
+
+__END_DECLS
+
+#endif