libroot: abort() should behave like a crash, not just a 'failure' exit.

Calling debugger() means that the crash dialog will be shown, and so
users will not be left wondering why an app just spontenously disappeared.

src/system/libroot/posix/stdlib/exit.cpp

@@ -289,7 +289,7 @@ abort()
 	fprintf(stderr, "Abort\n");
 
 	raise(SIGABRT);
-	exit(EXIT_FAILURE);
+	debugger("abort() called");
 }