dct/fft-test: use a replacement getopt() if the system has none present.

This allows compiling and running these tests on systems lacking a built-
in version of getopt(), such as MSVC.

Signed-off-by: Anton Khirnov <anton@khirnov.net>

configure

@@ -1083,6 +1083,7 @@ HAVE_LIST="
     fork
     getaddrinfo
     gethrtime
+    getopt
     GetProcessAffinityMask
     GetProcessMemoryInfo
     GetProcessTimes
@@ -2862,6 +2863,7 @@ check_func  fcntl
 check_func  fork
 check_func  getaddrinfo $network_extralibs
 check_func  gethrtime
+check_func  getopt
 check_func  getrusage
 check_struct "sys/time.h sys/resource.h" "struct rusage" ru_maxrss
 check_func  gettimeofday