In addition to Laszlo's commit fixing rhbz#928973, we can add
some compile-time assertion to lz_common.h to help catch similar
bugs in the future.
This uses gnulib's verify.h to make sure at compile-time that
the various constant arrays used in lz_common.h are of the expected
size.
I've checked that before Laszlo's patch, the assert triggers, and
that it's gone after it.
