examples: make them compile with compatibility functions disabled (Windows)

For MinGW this is `-DNO_OLDNAMES`, with MSVC it is
`-D_CRT_DECLARE_NONSTDC_NAMES=0`.

There have been some support for this before this patch.
After this patch this is extended to all examples.

(And also the standalone http/client programs, if here.)

Cherry-picked from #15652
Closes #15789

docs/examples/fileupload.c

@@ -30,6 +30,14 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 
+#ifdef _WIN32
+#undef stat
+#define stat _stat
+#undef fstat
+#define fstat _fstat
+#define fileno _fileno
+#endif
+
 int main(void)
 {
   CURL *curl;