CIOStream:
* Use flag based system instead (common flags are aliased; uses std::ios_base::openmode).
* 'ReadString' now writes into a string buffer (reference) that needs to be passed in by programmer (avoids copy).
* 'm_nSize' is now synced with any write operations.
CSigCache:
* Fixed bug causing crash when 'DecompressBlob' failed (results were never checked).
* Light formatting improvements.