This commit adds support for a new Environment Variable, SERVER_WAIT
which if set will cause the script to sleep for SERVER_WAIT seconds
before calling the wget executable. During this period, the custom
HTTP/HTTPS/FTP servers are all set up and running and can be used
for any other purposes. This feature is often used when a separate
executable must be used for testing apart from the one at src/wget
This eliminated the use of Global Variables from the HTTPServer module
and uses the more correct threading.Threads module to spawn a new
server. However, on multi-core systems, the performance may deteriorate
when too many servers are launched due to CPython implementation of GIL.
Many artefacts from the old model still remain, sometimes as commenst,
else as executable code. These will be cleaned up soon
