MinGW fixes, server port assigning cleanup and ping test cleanup. Fixes issue with visibility detection with MinGW. The visibility.m4 script was not actually trying to call the hidden function, which caused MinGW to detect improperly that visibility was supported. Fix for bogusFile on Windows build. Fixes to build warnings for unused variable 'res' and signed/unsigned comparison for sizeof min(). Cleanup of the server side port assignment to allow use with Windows/MinGW/Cygwin. If Windows uses new GetRandomPort() function in test.h to get port in in the 49152 - 65535 range. If *nix then uses the tcp_listen returned port. Otherwise uses the default wolfSSLPort. Refactor of the ping test code to use common file and properly handle ping count differences (Windows "-c" vs. *Nix style "-n"). Workaround for MinGW and cyassl/options.h getting file permissions error. Added non-fatal compile warning if using MinGW that "strtok_s" might be missing along with a link to public domain source that can be used.

testsuite/testsuite.c

@@ -332,6 +332,7 @@ void join_thread(THREAD_TYPE thread)
     assert(res == WAIT_OBJECT_0);
     res = CloseHandle((HANDLE)thread);
     assert(res);
+    (void)res; /* Suppress un-used variable warning */
 #endif
 }