rt: Set the stack depth limit to 1GB. Abort on error.

People hit the recursion depth limit too often, it's not possible
to unwind reliably from out-of-stack.

Issues rust-lang#3555, rust-lang#3695

src/rt/rust_env.cpp

@@ -97,7 +97,7 @@ get_max_stk_size() {
         return strtol(maxsz, NULL, 0);
     }
     else {
-        return 1024*1024*8;
+        return 1024*1024*1024;
     }
 }
 

src/rt/rust_task.cpp

@@ -530,11 +530,11 @@ rust_task::new_stack(size_t requested_sz) {
     // arbitrarily selected as 2x the maximum stack size.
     if (!unwinding && used_stack > max_stack) {
         LOG_ERR(this, task, "task %" PRIxPTR " ran out of stack", this);
-        fail();
+        abort();
     } else if (unwinding && used_stack > max_stack * 2) {
         LOG_ERR(this, task,
                 "task %" PRIxPTR " ran out of stack during unwinding", this);
-        fail();
+        abort();
     }
 
     size_t sz = rust_stk_sz + RED_ZONE_SIZE;