CMake coding style in ECM?

[Stephen Kelly]

Hi,

I propose using a modern CMake coding style in modules added to ECM. Notable 
changes compared to the only existing module in there not written from 
scratch (ECMOptionalAddSubdirectory):

* Use lowercase CMake commands
** if(...) instead of IF(...)
** add_subdirectory instead of ADD_SUBDIRECTORY(...)
** etc

* Use empty closing macros
** endif() instead of endif(...)
** endforeach instead of endforeach(...)

What do you think?

Steve.