C++ Network Library Code

- Added cgisupport.py, which contains http_headers class, which parses a string containing all headers and exposes them as a dictionary
- Renamed echo_form.py -> echo_body.py
- Polished POST tests

NEW: Tests of client POST functionality
NEW: CGI Python scripts to support POST tests
FIX: http_test_server.hpp now launches correct Python script on Windows as well
MOD: http_test_server.py now simply forwards all headers in an env var called HTTP_ALL_HEADERS as a simple string. Breaks the CGI abstraction, but preserves even custom headers.

Suppressed secure SCL warnings

More HTTP headers!

Added a new, more complete HTTP test python server.
Added example on how get the new HTTP headers.

Added copyright for Boost compliance and removed unnecessary include.

Fixing http_test_server.hpp to remove double patching result (oops).
Fixing http_test_server.hpp to not define the server_child member variable inline.
Fixing signedness comparison bug(s) in localhost_tests.cpp that show up with GCC.

Patch from Kim Grasman to mark expected failures from localhost_tests.cpp and factoring out http_test_server implementation to its own file.

1 line commit that allows the cgi app to return the headers requested by a client.

Note: This also suffers from bugs in implementation. Notably, the use of a default content-type header for the request.

Fixing bug which causes infinite loop in processing user-provided headers in http::client::create_request.