pgsql: Move FAQ_AIX information to installation instructions.

Log Message:
-----------
Move FAQ_AIX information to installation instructions.

The information on why the shared libraries are built the way they are
was not relevant to end users and has been made a mailing list archive
link in Makefile.shlib.

Modified Files:
--------------
pgsql/doc/src/sgml:
installation.sgml (r1.314 -> r1.315)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/installation.sgml?r1=1.314&r2=1.315)
pgsql/src:
Makefile.shlib (r1.117 -> r1.118)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/Makefile.shlib?r1=1.117&r2=1.118)

Removed Files:
-------------
pgsql/doc:
FAQ_AIX
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/FAQ_AIX)