tests/http_pipe.py: Python 3 support

The 2to3 tool converted socketserver (which I manually fixed up with an
import fallback) and the print(e) line. The xrange option was converted
to range, but it seems better to use the '*' operator here for
simplicity.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
cmake: build tool_hugehelp (ENABLE_MANUAL)

Rather than always outputting an empty manual page for the '-M' option,
generate a full manual page as done by autotools. For simplicity in
CMake, always generate the gzipped page as it will not be used anyway
when zlib is not available.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>