keep original C(XX)FLAGS also; nicer ICC setup branch; warn about missing optimization if CMAKE_BUILD_TYPE is not set.
keep original C(XX)FLAGS also; nicer ICC setup branch; warn about missing optimization if CMAKE_BUILD_TYPE is not set.

chr-engwer/Vc,VcDevel/Vc,VcDevel/Vc,chr-engwer/Vc,chr-engwer/Vc,VcDevel/Vc,VcDevel/Vc