CMake will no longer complain that the minimum CMake version is not specified for test/CMakeLists.txt.

Move `gtest_force_shared_crt` option to Win32 VC only.

Mentioned in #240

 * Support for both in-source and out-of-source builds
 * Set library version to 0.12 to map Debian package
 * Add separate options to build tests, examples and documentation
 * Add pkgconfig lookup support (if installed with `make install`)
 * Add CMake lookup support (if isntalled with `make install`)
 * Add Google Test Source lookup
 * Add CTest support for running tests (use `make test` or `ctest -V`)