pgsql: Fixed auto-prepare to not try preparing statements that are not

Log Message:
-----------
Fixed auto-prepare to not try preparing statements that are not preparable. Bug
found and solved by Boszormenyi Zoltan <zb@cybertec.at>, some small adjustments
by me.

Modified Files:
--------------
pgsql/src/interfaces/ecpg/preproc:
ecpg.addons (r1.11 -> r1.12)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/preproc/ecpg.addons?r1=1.11&amp;r2=1.12)
output.c (r1.25 -> r1.26)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/preproc/output.c?r1=1.25&amp;r2=1.26)
pgsql/src/interfaces/ecpg/test/expected:
preproc-autoprep.c (r1.6 -> r1.7)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/preproc-autoprep.c?r1=1.6&amp;r2=1.7)
preproc-autoprep.stderr (r1.6 -> r1.7)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/preproc-autoprep.stderr?r1=1.6&amp;r2=1.7)
preproc-autoprep.stdout (r1.1 -> r1.2)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/preproc-autoprep.stdout?r1=1.1&amp;r2=1.2)
sql-desc.c (r1.20 -> r1.21)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/sql-desc.c?r1=1.20&amp;r2=1.21)
sql-execute.c (r1.14 -> r1.15)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/sql-execute.c?r1=1.14&amp;r2=1.15)
sql-oldexec.c (r1.6 -> r1.7)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/sql-oldexec.c?r1=1.6&amp;r2=1.7)
thread-prep.c (r1.9 -> r1.10)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/thread-prep.c?r1=1.9&amp;r2=1.10)
thread-prep.stdout (r1.3 -> r1.4)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/thread-prep.stdout?r1=1.3&amp;r2=1.4)
thread-thread.stdout (r1.6 -> r1.7)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/thread-thread.stdout?r1=1.6&amp;r2=1.7)
thread-thread_implicit.stdout (r1.6 -> r1.7)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/thread-thread_implicit.stdout?r1=1.6&amp;r2=1.7)
pgsql/src/interfaces/ecpg/test/preproc:
autoprep.pgc (r1.2 -> r1.3)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/preproc/autoprep.pgc?r1=1.2&amp;r2=1.3)