pgsql: Added a configure test for "long long" datatypes.

Log Message:
-----------
Added a configure test for "long long" datatypes. So far this is only used in ecpg and replaces the old test that was kind of hackish.

Modified Files:
--------------
pgsql:
configure (r1.679 -> r1.680)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/configure?r1=1.679&r2=1.680)
configure.in (r1.627 -> r1.628)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/configure.in?r1=1.627&r2=1.628)
pgsql/config:
c-compiler.m4 (r1.20 -> r1.21)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/config/c-compiler.m4?r1=1.20&r2=1.21)
pgsql/src/include:
pg_config.h.in (r1.147 -> r1.148)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/pg_config.h.in?r1=1.147&r2=1.148)
pgsql/src/interfaces/ecpg/ecpglib:
extern.h (r1.40 -> r1.41)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/ecpglib/extern.h?r1=1.40&r2=1.41)
pgsql/src/interfaces/ecpg/include:
ecpg_config.h.in (r1.4 -> r1.5)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/include/ecpg_config.h.in?r1=1.4&r2=1.5)
pgsql/src/interfaces/ecpg/preproc:
ecpg.header (r1.15 -> r1.16)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/preproc/ecpg.header?r1=1.15&r2=1.16)