[OSM-dev] PBF format announcement. I am disabling the currently unused bzip2 and lzma features.

[Scott Crosby]

In order to simplify implementing PBF decoders, I have decided to
disable the use of bzip2 and lzma compression. Bzip2 has a poor
time/compression ratio tradeoff. I am marking it as obsolete and have
removed it from the *.proto definitions. LZMA is untested and
unproven. I am classifying it as a proposed extension. I am leaving it
in the *.proto definitions so that existing implementations will
compile, but there is no need for an implementation to support it. I
have updated the Wiki.

Osmosis's decoder has never supported bzip2 or lzma. Osmosis's pbf
writer --- the only pbf writer that I am aware of --- has also never
supported these formats. The only consequence of this change is that
existing decoders that support bzip2 will not compile correctly with
the new *.proto definitions until their bzip2 support is removed.

For now, the only compression features supported are no compression
and zlib, which are both required for a reader implementation.

Thanks, and sorry for making a format change, even if it is minor.
Scott