Patch from Dave Bremer

[markcmiller86]

Resolves #221

Fixes poorly designed freeing of file scope gloabls. Thanks to Dave Bremer.

While doing some testing, I found a memory error in DBClose(). I made a patch and wanted to offer it for inclusion in the Silo source. It's a two-line change, so I could hand it to you directly, or submit it through GitHub.

Current code:

        retval = (dbfile->pub.close) (dbfile);
        free(dbfile->pub.file_scope_globals);

Proposed change:

        SILO_Globals_t *tmp_file_scope_globals = dbfile->pub.file_scope_globals;
        retval = (dbfile->pub.close) (dbfile);
        free(tmp_file_scope_globals);

The dbfile->pub.close() function tends to call free on dbfile, so the pointer at dbfile->pub.file_scope_globals is in freed memory. It tends to work, unless you use a Windows debug build, or if you set MALLOCPERTURB on Linux, which writes a value into a freed buffe