Port seaf-server and httpserver to MinGW
Eliminate some warnings in Windows
[win] Use proper file system APIs.
Fix abug for pack source code
[server] Improve configure.ac

Add --enable-mysql config option.
[win] Fix a few bugs for server.

* evbuffer_write() doesn't work for file on Windows;
* bufferevent_new_socket() requires socket be non-blocking;
* Provide --disable-client config option on Windows;
* Remove --enable-httpserver config option, default when --enable-server is true.
Fix a typo
Fix a bug for make dist
Add api.py
Improve seafile_api
[client] Make sure only one seaf-daemon instance can run.
[client] Fix a few bugs.
Initialize logging early on start-up.
update version to 1.6.1
[client] Improve case conflict handling.
[mac] update to v1.6.1-mac
Add --ignore-errors option for GC.

This option asks GC program to ignore any I/O errors when reading
commit and fs objects.

Also improve logging output of GC program.
[client] Fix a GC bug.

Clone manager should set both REPO_LOCAL_HEAD and REPO_REMOTE_HEAD
properties after download is finished.
[client] Fix a bug in clone manager and GC.

After merging with an existing folder, create a "index" branch to
to refer to new changes from the worktree.

Previously we fulfill the same goal by forcing a commit operation
before setting repo->head. However the commit routine requires
repo->head and repo->worktree be set. This method is buggy and
doesn't work.
[client] Improve clone procudure.

* Set repo->worktree before setting repo->head.
* Don't check worktree on start-up if repo's head is not set.