pgsql: Document that configure option only affects contrib:

Log Message:
-----------
Document that configure option only affects contrib:

--with-ossp-uuid use OSSP UUID library when building /contrib/uuid-ossp

Modified Files:
--------------
pgsql:
configure (r1.568 -> r1.569)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/configure?r1=1.568&r2=1.569)
configure.in (r1.534 -> r1.535)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/configure.in?r1=1.534&r2=1.535)
pgsql/doc/src/sgml:
installation.sgml (r1.296 -> r1.297)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/installation.sgml?r1=1.296&r2=1.297)
pgsql/src/include:
pg_config.h.in (r1.125 -> r1.126)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/pg_config.h.in?r1=1.125&r2=1.126)