Partial fix for bug 2758 - Android issues with NDK r10c and API-21

Sylvain

When using API 21 and running on an old device (android < 5.0 ?) some function are missing.

functions are (at least) : signal, sigemptyset, atof, stpcpy (strcat and strcpy), srand, rand.


Very few modifications on SDL to get this working :

on SDL
======

Undefine android configuration :

HAVE_SIGNAL
HAVE_SIGACTION
HAVE_ATOF

In "SDL_systrhead.c", comment out the few block of lines with "sigemptyset".

Android.mk:
remove the compilation of "test" directory because it contains a few rand/srand calls

Also, there are more discussions about this in internet :
https://groups.google.com/forum/#!topic/android-ndk/RjO9WmG9pfE
http://stackoverflow.com/questions/25475055/android-ndk-load-library-cannot-locate-srand

src/thread/pthread/SDL_systhread.c

@@ -159,14 +159,15 @@ SDL_SYS_SetupThread(const char *name)
     }
 
    /* NativeClient does not yet support signals.*/
-#ifndef __NACL__
+#if !defined(__ANDROID__) && !defined(__NACL__)
     /* Mask asynchronous signals for this thread */
     sigemptyset(&mask);
     for (i = 0; sig_list[i]; ++i) {
         sigaddset(&mask, sig_list[i]);
     }
     pthread_sigmask(SIG_BLOCK, &mask, 0);
-#endif
+#endif /* !__ANDROID__ && !__NACL__ */
+
 
 #ifdef PTHREAD_CANCEL_ASYNCHRONOUS
     /* Allow ourselves to be asynchronously cancelled */