testsuite: Move complex tests to their own subdirectory

It seems a bit silly to isolate them by globbing vs "*complex*"
when we can just as easily put them in their own subdirectory.

testsuite/libffi.complex/return_complex.inc

@@ -0,0 +1,37 @@
+/* -*-c-*- */
+#include "ffitest.h"
+#include <complex.h>
+
+static _Complex T_C_TYPE return_c(_Complex T_C_TYPE c)
+{
+  printf ("%f,%fi\n", T_CONV creal (c), T_CONV cimag (c));
+  return 2 * c;
+}
+int main (void)
+{
+  ffi_cif cif;
+  ffi_type *args[MAX_ARGS];
+  void *values[MAX_ARGS];
+  _Complex T_C_TYPE c, rc, rc2;
+  T_C_TYPE cr, ci;
+
+  args[0] = &T_FFI_TYPE;
+  values[0] = &c;
+
+  /* Initialize the cif */
+  CHECK(ffi_prep_cif(&cif, FFI_DEFAULT_ABI, 1,
+		     &T_FFI_TYPE, args) == FFI_OK);
+
+  for (cr = -127.0; cr <  127; cr++)
+    {
+      ci = 1000.0 - cr;
+      c = cr + ci * I;
+      ffi_call(&cif, FFI_FN(return_c), &rc, values);
+      rc2 = return_c(c);
+      printf ("%f,%fi vs %f,%fi\n",
+	      T_CONV creal (rc), T_CONV cimag (rc),
+	      T_CONV creal (rc2), T_CONV cimag (rc2));
+      CHECK(rc == 2 * c);
+    }
+  exit(0);
+}