Library:
 * Better error handling.
 * Extract:
    * Add options API to control whether permissions, timestamp are set.
    * Creation of parent directories on extract (+optional)
 * Add LHAFile convenience class.
 * Compression and LHA file generation.
 * MacBinary header detection and removal, to support MacLHA archives.
 * Decompressors for obscure algorithms (need to write compressors):
    * -lh2-, -lh3- (experimental LHA?)
    * -pm1- (Old PMArc)
 * Conditional compile to remove POSIX dependency.  Add Windows build.

Command line tool:
 * Create/update/modify archives.

Testing:
 * Valgrind.
 * Improve coverage.

