Add unit test for wxWebRequest

The environment variable WX_TEST_WEBREQUEST_URL has to
be set to https://httpbin.org or a local instance of it
to be run.

build/cmake/tests/base/CMakeLists.txt

@@ -52,6 +52,7 @@ set(TEST_SRC
     misc/typeinfotest.cpp
     net/ipc.cpp
     net/socket.cpp
+    net/webrequest.cpp
     regex/regextest.cpp
     regex/wxregextest.cpp
     scopeguard/scopeguardtest.cpp