use GLEW::GLEW imported target to fix builds on openSUSE Tumbleweed (#428)

* CMake 3.1 (2014) introduced the GLEW::GLEW imported target in FindGLEW. This provides a more robust linking target than relying on the old GLEW_LIBRARIES variable

* the build script checked for Wayland packages (pkg_check_modules) but did not actually add the found include directories to the compiler path. this commit adds  `include_directories(${WAYLAND_SUPPORT_INCLUDE_DIRS})` in the Wayland configuration block.

CMakeLists.txt

@@ -165,6 +165,7 @@ if(WAYLAND_SUPPORT_FOUND)
         COMMAND ${WaylandScanner} private-code ${WAYLAND_PROTOCOLS_DIR}/stable/xdg-shell/xdg-shell.xml ${WAYLAND_OUTPUT_DIR}/xdg-shell-protocol.c)
 
     add_compile_definitions(ENABLE_WAYLAND)
+    include_directories(${WAYLAND_SUPPORT_INCLUDE_DIRS})
     include_directories(${WAYLAND_OUTPUT_DIR})
     set(WAYLAND_LIBRARIES
         pthread
@@ -472,7 +473,7 @@ add_executable(
 
 target_link_libraries (linux-wallpaperengine PUBLIC
     ${OPENGL_LIBRARIES}
-    ${GLEW_LIBRARIES}
+    GLEW::GLEW
     ${GLUT_LIBRARIES}
     ${ZLIB_LIBRARIES}
     ${LZ4_LIBRARY}