To know root cause of exception:
* src/Exception.h
(cause): New variable.
(Exception): Added a parameter.
(getMsg): Return const reference to msg.
(getCause): New function.
* src/DlRetryEx.h
(DlRetryEx): Added a parameter 'cause'.
Added an overloaded constructor.
(DlAbortEx): Added a parameter 'cause'.
Added an overloaded constructor.
* src/SimpleLogger.cc
(writeLog): Log nested exception messages recursively.
* CookieBox.cc: rewrited criteriaFind() using Util::startsWith()
and
Util::endsWith().
* SocketCore.cc: struct addrinfo is now zero-initialized.
* common.h: added #include directive of limit.h.
* DownloadEngine.cc: added #include directive of sys/time.h and
algorithm.
* Exception.h: added #include directive of stdio.h.
* AbstractCommand.h: added #include directive of sys/time.h.
* DownloadCommand.h: added #include directive of sys/time.h.
* *.h: added #include directive of common.h to all base classes.
subclasses' one was removed.