iphone: Ruby VM make time_t unsigned to expand date capacity
#define NUM2GIDT(v) NUM2UINT(v)
#define PRI_GIDT_PREFIX PRI_INT_PREFIX
#define rb_time_t time_t
-#define SIGNEDNESS_OF_TIME_T -1
+#define SIGNEDNESS_OF_TIME_T 1
#define TIMET2NUM(v) LONG2NUM(v)
#define NUM2TIMET(v) NUM2LONG(v)
#define PRI_TIMET_PREFIX PRI_LONG_PREFIX
