Since typelib ids are recorded as a GuidAttribute on an assembly, any
guids from other CustomAttribute entries that are not on an assembly and
are not constructed from a MemberRef can be discarded.

MemberRef can be used to filter because GuidAttribute comes from
mscorlib, so unless we're looking at mscorlib itself GuidAttribute will
always be constructed using a MemberRef into another assembly.

If higher-index tables were not present, but their row count affects a
coded index, the row_count array may not have been large enough to index
for all tables the coded index can reach.

As a fix, ensure the row_count table is always 64 entries.