MySQL fixes/additions/improvements

- fixed GH #187: MySQL: allow access to the underlying connection handle
- added GH #186: MySQL: support for MYSQL_SECURE_AUTH
- fixed GH #174: MySQL: 4GB allocated when reading any largetext or
largeblob field
WinCE fixes for zlib 1.2.8
fix MySQLTest info calls
updated version to 1.5.2
Solaris build
Don't call CloseHandle() twice on Windows (as it causes crashes, or unexpected behavior). This would happen with the following test case:
ProcessHandle handle = Process.launch(...);
handle.kill();
Then as handle gets out of scope, ~ProcessHandle would call CloseHandle() on an already closed handle.
Add operators to Timestamp for Timespan.

Timestamp  operator +  (const Timespan& span) const;
Timestamp  operator -  (const Timespan& span) const;
Timestamp& operator += (const Timespan& span);
Timestamp& operator -= (const Timespan& span);
Merge pull request #180 from syvex/TimestampTimespanOperators

Add operators to Timestamp for Timespan.
added coding style guide
Allow RemoteSyslogChannel to be used again after being closed.
Remove the need for a debug build or debugger when setting POSIX thread names.
Remove the need for a debug build or debugger when setting Win32 thread names.
Integrate Poco::Web::JSON parser
Merge pull request #200 from fbraem/develop

Integrate Poco::Web::JSON parser
JSON fixes/refactoring
Foundation/include/Poco/Platform.h: Add support for AArch64.

Add support for big and little endian AArch64 preprocessor defines.
Merge pull request #203 from willnewton/develop

Foundation/include/Poco/Platform.h: Add support for AArch64.
Ability to select the threadpool that will be used to start an Activity.
fixed GH# 173: HTTPClientSession::proxyConnect forces DNS lookup of host names
fixed GH# 194: MessageNotification constructor is inefficient.