Modify several tests to use test-skeleton.c

These tests were skipped by the use-test-skeleton conversion done in
commit 29955b5d because they did not have an `int main (void)'
declaration. Instead their `main' functions were declared with arguments
(i.e. argc, argv) even though they didn't use them.

Remove these arguments and include the test skeleton in these tests.

stdio-common/test-fwrite.c

@@ -1,8 +1,8 @@
 #include <stdio.h>
 #include <string.h>
 
-int
-main (int argc, char *argv[])
+static int
+do_test (void)
 {
   FILE *f = tmpfile ();
   char obuf[99999], ibuf[sizeof obuf];
@@ -66,3 +66,6 @@ There is absolutely no warranty for GDB; type \"show warranty\" for details.\n\
   puts ("Test succeeded.");
   return 0;
 }
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"