3 bugfixes for WOAdaptor

Hi,

1. 
calling http-Sources for Adaptor config using the ifNotModifiedSince-Header was a bad idea,
as merging the config from changed and unchanged sources does not work properly. Probably
almost nobody makes use of http sources (but me), but its a fixed bug, anyway.

2. 
IIS 7 has a serious issue on streaming downloads. This fix enforces IIS 6 behaviour and ensures
proper download streaming.

3. 
Bugfix for appcfg.c where a config server that becomes unavailable might crash your webserver.
assigning  "buffer[i] = NULL" ensures that this pointer is not used uninitialized!

A new version number identifies this version.

When then change is accepted, I will supply the new IIS binaries to Pascal

Regards, Markus