Make check for WITH_MLED non-fatal

There is no reason for the configuration check to be fatal, because the
system the package builds on may be different from the one that it will
run on.

On the other hand the flag is pretty useless nowadays anyway, so print a
hefty warning if the interface is missing.

Signed-off-by: Alexander Golubev <fatzer2@gmail.com>

ConfigureChecks.cmake

@@ -45,9 +45,17 @@ endif( WITH_SSL )
 #### check for ASUS Mail LED
 
 if( WITH_MLED )
-  if( EXISTS "/proc/acpi/asus/mled" )
-    set( HAVE_MLED 1 )
-  else( )
-    tde_mesage_fatal( "ASUS Mail LED support was requested but not found in ACPI" )
+  set( HAVE_MLED 1 )
+  if( NOT EXISTS "/proc/acpi/asus/mled" )
+      message( WARNING
+          "\n"
+          "-DWITH_MLED=ON requires 'asus-laptop' kernel module from acpi4asus "
+          "project to work, which was not found on your system. The project is "
+          "currently abandoned and the module doesn't support linux kernels above "
+          "2.6.19. There is no harm in enabling the flag besides an additional "
+          "message on stderr, but you won't get any benefits from it either unless "
+          "you run some very unusual system configuration."
+          "\n"
+      )
   endif( )
 endif( WITH_MLED )