Rename add_icon_c_test

Here we discuss whether we should rename the CMake macro add_icon_c_test.
Discussion moved from !35 (comment 182420)

mentioned in merge request !35 (merged)

Does this need a discussion at all? You get the answer as soon as there's a decision on #9. Basically, we need to decide on prefixes for project-specific CMake variables/macros/functions.

closed