Revert "Fix: typo: DECLARE_URCU_TLS_IE -> DEFINE_URCU_TLS_IE"

This reverts commit 364979886a80f7c993b3210af48a93f7d65f4530.

The initial-exec model seems to behave differently than global-dynamic
with respect to lazy initialization, causing locks to be taken then
first time each thread touch the TLS. This introduces deadlocks with
library constructors waiting on other threads.

This will require further investigation.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>