ERROR from pg_restore - From OS X to Ubuntu

I dumped from:
OS: OS X 10.5.8
pg version: PostgreSQL 9.0.4 on x86_64-apple-darwin, compiled by GCC
i686-apple-darwin10-gcc-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5664), 64-bit
Installation Method: EDB installer

to:
OS: Ubuntu 10.04.3 64bit
pg version: PostgreSQL 9.1.1 on x86_64-pc-linux-gnu, compiled by
gcc-4.4.real (Ubuntu 4.4.3-4ubuntu5) 4.4.3, 64-bit
installation Method: apt-get install postgresql-9.1 postgresql-contrib-9.1

During the restoration I got the following errors:

ERROR: could not access file "$libdir/targetinfo": No such file or
directory
ERROR: function public.pldbg_get_target_info(text, "char") does not exist
ERROR: could not access file "$libdir/plugins/plugin_debugger": No such
file or directory
ERROR: function public.plpgsql_oid_debug(oid) does not exist

My question is:
1. Is this safe to ignore? I don't recall using any of the function
2. If not, how can I install those missing libraries?

Thank you very much for your time in advance.

Naoko