pgsql: Allow SQL:2008 syntax ALTER TABLE ...

Log Message:
-----------
Allow SQL:2008 syntax ALTER TABLE ... ALTER COLUMN ... SET DATA TYPE
alongside our traditional syntax.

Modified Files:
--------------
pgsql/doc/src/sgml/ref:
alter_table.sgml (r1.99 -> r1.100)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/alter_table.sgml?r1=1.99&r2=1.100)
pgsql/src/backend/catalog:
sql_features.txt (r1.22 -> r1.23)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/sql_features.txt?r1=1.22&r2=1.23)
pgsql/src/backend/parser:
gram.y (r2.626 -> r2.627)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y?r1=2.626&r2=2.627)
keywords.c (r1.202 -> r1.203)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/keywords.c?r1=1.202&r2=1.203)
pgsql/src/interfaces/ecpg/preproc:
ecpg_keywords.c (r1.38 -> r1.39)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/preproc/ecpg_keywords.c?r1=1.38&r2=1.39)
preproc.y (r1.376 -> r1.377)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/preproc/preproc.y?r1=1.376&r2=1.377)
pgsql/src/interfaces/ecpg/test/expected:
sql-parser.c (r1.4 -> r1.5)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/sql-parser.c?r1=1.4&r2=1.5)
sql-parser.stderr (r1.5 -> r1.6)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/sql-parser.stderr?r1=1.5&r2=1.6)
pgsql/src/interfaces/ecpg/test/sql:
parser.pgc (r1.1 -> r1.2)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/sql/parser.pgc?r1=1.1&r2=1.2)