Use Apple libtool when building static lib using Makefile. Closes #74.

Also in the commit:
- Remove BOM from License.txt and Readme.txt. Update Urho3D website URL in Readme.txt.
- Detect MSYS build environment. It is now possible to build Urho3D using Msys shell on Windows, i.e. cmake_gcc.sh could be used for both native build and Android build on Windows platform (MinGW is required).