cmake: Fix configured devices output for wayland extras.

1) Fix display of wayland extras support.  This value had also been
   changed from a global to a target specific definition.

2) Change local variables to begin with an underscore.

mythtv/cmake/PrintConfig.cmake

@@ -156,8 +156,8 @@ if(ENABLE_FRONTEND)
   message_trgt("x11/xrandr support      " X11::Xrandr)
   if(TARGET X11::X11)
     message_trgt("VDPAU support           " PkgConfig::VDPAU)
-    get_target_property(FFNVCODEC_DEFS PkgConfig::FFNVCODEC INTERFACE_COMPILE_DEFINITIONS)
-    if("USING_NVDEC" IN_LIST FFNVCODEC_DEFS)
+    get_target_property(_FFNVCODEC_DEFS PkgConfig::FFNVCODEC INTERFACE_COMPILE_DEFINITIONS)
+    if("USING_NVDEC" IN_LIST _FFNVCODEC_DEFS)
       set(_USING_NVDEC ON)
     endif()
     message_vrbl("NVDEC support           " _USING_NVDEC)
@@ -194,7 +194,13 @@ message("# Misc Features")
 message_vrbl("Frontend                " ENABLE_FRONTEND)
 message_vrbl("Backend                 " ENABLE_BACKEND)
 message_trgt("Qt private headers      " Qt${QT_VERSION_MAJOR}::GuiPrivate)
-message_vrbl("Wayland extras          " USING_WAYLANDEXTRAS)
+if(TARGET PkgConfig::WAYLAND_CLIENT)
+  get_target_property(_WAYLAND_DEFS PkgConfig::WAYLAND_CLIENT INTERFACE_COMPILE_DEFINITIONS)
+  if("USING_WAYLANDEXTRAS" IN_LIST _WAYLAND_DEFS)
+    set(_USING_WAYLANDEXTRAS ON)
+  endif()
+endif()
+message_vrbl("Wayland extras          " _USING_WAYLANDEXTRAS)
 message("multi threaded libavcodec ${threads-no}")
 if(USING_FRONTEND)
   message_trgt("libxml2 support         " PkgConfig::LibXml2