The attached patch fixes the following problems:

+ gstfileindex tries to allocate writer_ids even if the index is empty
(reverse logic).

+ g_array_index didn't do what i expected.  Pass an explicit stride around
to  calculate record offsets.

+ Store index records in increasing order instead of decreasing.

+ Use temporaries for most GINT64_TO/FROM_BE macros.  This probably isn't
needed but it makes it easier to understand and debug.

+ Fix the indexers testsuite so it compiles again.  Pass memindex or
fileindex on the command line.

+ In cache1.c, compare actual results with expected results.