Fix macro-redefinition warning on MSVC.
Fix macro-redefinition warning on MSVC.

In commit 9d6b160d7, I tweaked pg_config.h.win32 to use
"#define HAVE_LONG_LONG_INT_64 1" rather than defining it as empty,
for consistency with what happens in an autoconf'd build.
But Solution.pm injects another definition of that macro into
ecpg_config.h, leading to justifiable (though harmless) compiler whining.
Make that one consistent too.  Back-patch, like the previous patch.

Discussion: d57a92db5c587136c03897dbc2a317f1f197ad8d@mail.gmail.com

xinzweb/gpdb,greenplum-db/gpdb,xinzweb/gpdb,greenplum-db/gpdb,50wu/gpdb,xinzweb/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,50wu/gpdb,50wu/gpdb,adam8157/gpdb,adam8157/gpdb,50wu/gpdb,xinzweb/gpdb,adam8157/gpdb,lisakowen/gpdb,50wu/gpdb,lisakowen/gpdb,greenplum-db/gpdb,lisakowen/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,xinzweb/gpdb,greenplum-db/gpdb,adam8157/gpdb,adam8157/gpdb,adam8157/gpdb,50wu/gpdb,adam8157/gpdb,50wu/gpdb,lisakowen/gpdb,adam8157/gpdb,lisakowen/gpdb,lisakowen/gpdb,50wu/gpdb,lisakowen/gpdb,xinzweb/gpdb,xinzweb/gpdb,lisakowen/gpdb,xinzweb/gpdb