Where is pgplsql.so located in 7.1.2?

When I do

createlang -U postgres -d mydbname pgplsql mydbname
I got can't find /usr/share/pgsql/plpgsql.so error message.

But there is no plpgsql.so file in /usr/share/pgsql directory!
I just installed RPM binary 7.1.2 for Redhat 6.2

In 7.0 the pgplsql.so file is located in /usr/lib/pgsql/
So I do

createlang -U postgres -d mydbname --pglib=/usr/lib/pgsql pgplsql
mydbname

Then I got
A function named plpgsql_call_handler already exists. Installation
abort.

But createlang -l mydbname shows there is nothing there.
Shall I do
drop function plpgsql_call_handler; ?
Or where I can find plpgsql.so file for 7.1.2 in /usr/share/pgsql/ ?

Please don't tell me I need to compile PostgreSQL by myself order to get
all
*.so files.

--Raymond