build_system: mark libfdk as non GPL compatible until the situation is...

build_system: mark libfdk as non GPL compatible until the situation is clarified by someone qualified.

The license fee text may be interpreted as a additional restriction in the GPL sense.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

configure

@@ -2928,6 +2928,7 @@ die_license_disabled gpl x11grab
 die_license_disabled nonfree libaacplus
 die_license_disabled nonfree libfaac
 enabled gpl && die_license_disabled_gpl nonfree openssl
+enabled gpl && die_license_disabled_gpl nonfree libfdk_aac
 
 die_license_disabled version3 libopencore_amrnb
 die_license_disabled version3 libopencore_amrwb