protobuf-c.c: Fix repeated field concatenation order in merge_messages (fixes #147)
Revert "protobuf-c: Add vim modeline magic at the end of the files"

This reverts commit e7dc76c54bf5869247ec0a330ae9cf7f5499154d.

i really dislike cluttering up files with editor-specific modelines, and
anyway the //-comments run afoul of #124.