ecpg: Remove trailing period from error message.

This commit improves the ecpg's error message that commit f576de1db1 updated,
so that it gets rid of trailing period and uppercases the command name
in the error message.

Back-patch to v14 where the error message exists.

Author: Kyotaro Horiguchi
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/20210819.170315.1413060634876301811.horikyota.ntt@gmail.com

src/interfaces/ecpg/preproc/ecpg.header

@@ -596,7 +596,7 @@ check_declared_list(const char *name)
 		{
 			if (connection)
 			if (connection && strcmp(ptr->connection, connection) != 0)
-				mmerror(PARSE_ERROR, ET_WARNING, "connection %s is overwritten with %s by declare statement %s.", connection, ptr->connection, name);
+				mmerror(PARSE_ERROR, ET_WARNING, "connection %s is overwritten with %s by DECLARE statement %s", connection, ptr->connection, name);
 			connection = mm_strdup(ptr -> connection);
 			return true;
 		}