Added Mutex.new statement to prevent deadlocking error

[bootstraponline]

From @saranyan on June 16, 2011 18:9

Hi, in ruby 1.9, there were errors when I tried to use the gem.
internal:prelude:8:in `lock': deadlock; recursive locking (ThreadError)
I traced it to base.rb statement - @mailbox_mutex.synchronize do
This does not make sense to me as it should be a mutex variable. I just made this into mutex variable and the errors went away. Thought this might be useful to others.

thanks!
great Gem. very useful. thanks :)

Copied from original issue: nu7hatch/gmail/pull/28

[bootstraponline]

From @nu7hatch on August 17, 2011 18:38

deadlocking went away, but this solution breaks thread-safety. I think for this line i will just revert thread safety additions, and move work on it to a separate branch. Anyway, thanks for the help!

[bootstraponline]

From @nu7hatch on August 17, 2011 18:47

Ok, so i'm closing this pull req without merging. Keep an eye on this issue nu7hatch/gmail#34

[bootstraponline]

From @zenzei on July 5, 2012 18:36

I was having the same problem and this workaround help me in a ruby 1.9.3p125 (I understand is not thread safe, but I could live without it for a while).