modified some functions in string_util
working on trying to add a light-weight i.e. thread-boundary lock
add thread-boundary lock for logging when USE_LOCAL_LOCK flag is set
A generic ScopedHandle class for HANDLE or FILE*

1.Traits class for two fundamental handle type(HANDLE and FILE*) are provided.
2.bare-bone for ScopedHandle class.
working on ScopeHandle
done with ScopedHandle.
modified with scoped_handle
1. bugfix: operator=(ScopedHandle&& rhs) causes original handle being deleted.
2. makes conversion to Handle explicit; and correct spelling.
3. add unittest for ScopedHandle.
modified in scoped_handle
1. bugfix: move-assignment didn't close old handle.
2. added: make Traits class abstract
3. added: make ScopedHandle non-copyable.
modified in logging
1. modified: replace raw FILE* with ScopedStdioHandle