ENH: Add buffer based IO support

[MarkPundurs]

This would allow language wrapping libraries such as pyreadstat to use a memory buffer instead of a file on disk as source. (#179 tried to address this, but checks failed.)

[ofajardo]

In pyreadstat, this should be now solved in version 1.3.3 via Roche/pyreadstat#309 using only the already available functions. Big thanks to @slobodan-ilic for the implementation!