Open BMP with header size 108 bytes

PIL doesn't support
http://msdn.microsoft.com/en-us/library/windows/desktop/dd183380%28v=vs.85%29.aspx

This header is very similar to this one
http://msdn.microsoft.com/en-us/library/windows/desktop/dd183376%28v=vs.85%29.aspx

With given changes its possible to open and manipulate BMP file with
header size of 108 bytes.