TCPServer: do not reduce the capacity of the default ThreadPool
Add a POCO_LOG_DEBUG flag

If the POCO_LOG_DEBUG is defined the poco_trace* and the poco_debug*
produce logs even if the _DEBUG flag is not set.
This makes the macros usable for applications that need to enable
higher log levels later at run time.
fixed thread priority issues on POSIX platforms with non-standard scheduling policy
Merge pull request #421 from siemens/debug-log

Add a POCO_LOG_DEBUG flag
Zip: fixed a crash caused by an I/O error (e.g., full disk) while creating a Zip archive
Merge remote-tracking branch 'upstream/develop' into develop