Pulled the conversion between seconds since the epoche and the split up

(year, month,...) representation out of the x86 specific code and put
respective support functions into real_time_clock.c. We'll need those
for the PPC specific part too.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@15827 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/real_time_clock.h

@@ -8,6 +8,10 @@
 
 #include <KernelExport.h>
 
+#include <time.h>
+
+
+#define RTC_EPOCHE_BASE_YEAR	1970
 
 #ifdef __cplusplus
 extern "C" {
@@ -26,6 +30,11 @@ typedef struct rtc_info {
 
 status_t get_rtc_info(rtc_info *info);
 
+// Both functions use the passed struct tm only partially
+// (no tm_wday, tm_yday, tm_isdst).
+uint32 rtc_tm_to_secs(const struct tm *t);
+void rtc_secs_to_tm(uint32 seconds, struct tm *t);
+
 bigtime_t _user_system_time(void);
 status_t _user_set_real_time_clock(uint32 time);
 status_t _user_set_timezone(int32 timezoneOffset, bool daylightSavingTime);