cmake: tidy-up foreach() syntax

Use `IN LISTS` and `IN ITEMS`. This appears to be the preferred way
within CMake's own source code and possibly improves readability.

Fixup a side-effect of `IN LISTS`, where it retains empty values at
the end of the list, as opposed to the syntax used before, which
dropped it. In our case this happened with lines read from a text
file via `file(READ)`.

https://cmake.org/cmake/help/v3.7/command/foreach.html

Closes #1180

cmake/CheckFunctionExistsMayNeedLibrary.cmake

@@ -65,7 +65,7 @@ function(check_function_exists_may_need_library function variable)
   check_function_exists(${function} ${variable})
 
   if(NOT ${variable})
-    foreach(lib ${ARGN})
+    foreach(lib IN LISTS ARGN)
       string(TOUPPER ${lib} UP_LIB)
       # Use new variable to prevent cache from previous step shortcircuiting
       # new test