Add additional search paths for glog & Eigen on Windows.

- When built with CMake on Windows, the default install prefix
  will be C:/Program Files/<PROJECT_NAME> (instead of /usr/local on
  Linux / OS X.
- Due to an upstream change in Eigen >= 3.3, the project name for Eigen
  changed to Eigen3 from Eigen, thus changing the default install
  location.
- glog, uses the project name “google-glog”, thus when it is build with
  CMake, this becomes it’s default install path instead of just glog
  when built with other tools.
- This patch adds both of these paths to the default search list on
  Windows.

Change-Id: I987b502fed0f6e685c504fd47fd504307aad8bef