note that SSL_library_init() is not reentrant

doc/ssl/SSL_library_init.pod

diff --git a/doc/ssl/SSL_library_init.pod b/doc/ssl/SSL_library_init.pod
index ecf3c48..eed526e 100644
--- a/doc/ssl/SSL_library_init.pod
+++ b/doc/ssl/SSL_library_init.pod
@@ -23,6 +23,7 @@
 =head1 NOTES
 
 SSL_library_init() must be called before any other action takes place.
+SSL_library_init() is not reentrant. 
 
 =head1 WARNING