CMake: rename CMake project to "rebol3"

Some generators (such as Eclipse) work better with distinct names for
project and executable targets.
CMake: use r3-make for bootstrapping

Use "r3-make" (not "rebol3") for code generation in the "prepare" phase,
like in the mainline makefiles.
CMake: fix dependency from "r3" on "prepare" for MSVS

The MS Visual Studio generator does not take dependencies between files
in different targets into account. It creates one "project" for each
target, but does not life file-level dependencies to project-level
dependencies.

To fix this, we add an explicit dependency from "r3" on "prepare" when
targeting MSVC.