Get rid of tempnam()
Get rid of tempnam()

```
warning: the use of `tempnam' is dangerous, better use `mkstemp'
```

It is annoying, and could not be suppressed since it's a linker warning.
`-Wno-deprecated-declarations` has no effect, and overriding the
`.gnu.warning.foobar` binary section doesn't work with other compilers.

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