cmake scripts enhancements

[Marcin Wojdyr]

I'd like to propose two changes to cmake script, but before making PR I'd like to ask what you think about it.

• FindFreetype.cmake - the version of this file distributed with cmake does more robust search for headers and library. It'd be easy to replace or remove this script from libgd unless there are some essential customizations. I think there are none, but I may be wrong.

• more control what is built: options BUILD_SHARED_LIBRARY, BUILD_STATIC_LIBRARY, BUILD_PROGRAMS

[Pierre Joye]

It is mainly about checking for the right lib name on Windows where we habe freetype_a or freetype. But I have to update these files using the latest versions and add some.

[Pierre Joye]

fixed in master, will be in next 2.1.0. Thanks for your report!

[Marcin Wojdyr]

Thanks for your work!