JL_THREAD -> JL_THREAD_LOCAL

This code is currently dead on all supported platforms,
which is why nobody noticed this breakage, but thread locality
is annotated using the `JL_THREAD_LOCAL` macro these days,
not the `JL_THREAD` macro (which no longer exists).

Author: Keno

src/task.c

@@ -70,7 +70,7 @@ static void jl_start_fiber(jl_ucontext_t *lastt, jl_ucontext_t *t);
 static void jl_swap_fiber(jl_ucontext_t *lastt, jl_ucontext_t *t);
 
 #ifdef JL_HAVE_UNW_CONTEXT
-static JL_THREAD unw_cursor_t jl_basecursor;
+static JL_THREAD_LOCAL unw_cursor_t jl_basecursor;
 #endif
 
 #ifdef ALWAYS_COPY_STACKS