FindZLIB: Add imported target and documentation
FindGLEW: Add imported target and documentation
FindX11: fix documentation formatting error

While at it, remove excess indentation.
Merge topic 'find-module-targets' into next

c90c7fca FindX11: fix documentation formatting error
3d82a223 FindGLEW: Add imported target and documentation
5a7ff421 FindZLIB: Add imported target and documentation