Set curl build options as needed for CMake rather than presenting them
to the user in the cache. Drop the CMAKE_BUILD_CURL_SHARED option for
now.
Change the curl library name to 'cmcurl'. Disable blocks of code within
curl CMakeLists.txt files that we do not need for CMake, but leave the
code in place to make merging with curl updates easier.
The resource file is only needed for the curl .dll, so skip it when
building the static library. This avoids the need to add the
'/machine:' link flag on MS tools for creating a static library.
Brad King