[CMake] FAQ update for renaming a library

[Brandon J. Van Every]

I am questioning the relevance or clarity of this FAQ entry:
http://www.cmake.org/Wiki/CMake_FAQ#How_do_I_rename_a_library_that_has_already_been_built.3F
This looks like some kind of historical hack-around.  I don't think we 
want to be telling people to rename libraries.  Rather, we should be 
telling them how to generate targets with different OUTPUT_NAMEs, 
prefixes, postfixes, etc.

I will make necessary changes / slaughterings if we agree the stuff 
about renaming should go away.

Cheers,
Brandon Van Every