Implement support code for the testing of WSGI handlers/servers.

[albu-diku]

Depends on: #134

[jonasbardino]

Is this one still relevant @albu-diku or was it obsoleted by the merge of PR #98 ? I noticed this is against edge so not sure.
Please also address the uninitialized fake.calls issue here (see PR #193) if so.

[albu-diku]

Is this one still relevant @albu-diku or was it obsoleted by the merge of PR #98 ? I noticed this is against edge so not sure. Please also address the uninitialized fake.calls issue here (see PR #193) if so.

@jonasbardino this was originally just a split out version of what the same file in #98, partly intended in more regularly merging smaller pieces and partly because it was consumed in a lot of other places. I think this can be closed, and my temptation is to action that now, but it is probably worth a diff of the file to ensure everything contained here is already in-tree. Will do that offline.