rename files with OS specific request test code

Added _test so they will only be compiled as part of the tests.
diff --git a/request-unix.go b/request-unix_test.go
similarity index 100%
rename from request-unix.go
rename to request-unix_test.go
diff --git a/request_windows.go b/request_windows_test.go
similarity index 100%
rename from request_windows.go
rename to request_windows_test.go