Fix shared module generation on AIX bug #77676

Fix shared module generation on AIX bug #77676

Makefiles for PHP extensions generated by phpize expect the PHP_MODULES
to contain a list of libtool .la files so that it can read the $dlname
variable from them by sourcing them in to a shell. On AIX, the code was
setting PHP_MODULES to a list of .so files, which meant the dlname was
blank, preventing the tests from being able to run.

Change the AIX code path in the PHP_SHARED_MODULE macro to match the
output on other platforms, using libtool .la files.