[postgis-devel] $libdir and pg_config --pkglibdir compatibility

[strk]

PG7.2 documentaions explains that IF you specify a library to be
loaded without a trailing '/' that lib is searched in the directories
specified by the run-time configuration directive DYNAMIC_LIBRARY_PATH,
which defaults to just $libdir, which in turn resolves to what
pg_config --pkglibdir reports.

PG7.1 documentation says nothing about $lidir, and does not list
--pkglibdir among its valid arguments.

This means that PG7.1 can not have this nice mobility feature.
But from PG7.2 on we can use pg_config --pkglibdir (or a more
internal equivalent variable) to find library installation prefix.

NOTE that current behaviour is rely on postgresql Makefile for
     the install-lib rule. If the author of this file is still
     around I'd ask him/her for help about this.

--strk;