LibC: Make errno macro directly access uthread

This allows inlining errno usages

This breaks libc ABI and requires toolchain rebuild

userspace/libraries/LibC/include/errno.h

@@ -7,6 +7,10 @@
 
 __BEGIN_DECLS
 
+#include <bits/types/uthread.h>
+
+#define errno (_get_uthread()->errno_)
+
 #define E2BIG			1
 #define EACCES			2
 #define EADDRINUSE		3
@@ -94,10 +98,6 @@ __BEGIN_DECLS
 #define ERESTART        0xFE /* internal errno for SA_RESTART */
 #define EUNKNOWN		0xFF
 
-#define errno (*__errno_location())
-
-int* __errno_location(void);
-
 __END_DECLS
 
 #endif