Claudio authored Mar 13, 2019 and Brad King committed Mar 15, 2019

Replicate behaviour of upstream GLEW.

* define the imported target GLEW::glew for the shared library GLEW

* if GLEW_USE_STATIC_LIBS is defined and set to TRUE, this module instead
  defines the imported target GLEW::glew_s for the static library GLEW

* an imported target GLEW::GLEW is created as a copy of either GLEW::glew
  or GLEW::glew_s

* by setting GLEW_VERBOSE you print out the log of the module.

Fixes: #17638, #17864, #18989