[PATCH] Do date parsing by hand...

...since everything out there is either strange (libc mktime has issues
with timezones) or introduces unnecessary dependencies for people (libcurl).

This goes back to the old date parsing, but moves it out into a file of
its own, and does the "struct tm" to "seconds since epoch" handling by
hand. 

I grepped through the tz-database and it seems there's one "country"
left that has non-60-minute DST: Lord Howe Island.  All others dropped
that before 1970.

cache.h

@@ -148,6 +148,9 @@ extern void *read_object_with_reference(const unsigned char *sha1,
 					unsigned long *size,
 					unsigned char *sha1_ret);
 
+void parse_date(char *date, char *buf, int bufsize);
+void datestamp(char *buf, int bufsize);
+
 static inline void *xmalloc(int size)
 {
 	void *ret = malloc(size);