do not make DaysInMonth static

Since the Feb month is written to based on arguments to this function,
it makes it not safe to use simultaneously.  Drop the static markings.
diff --git a/libarchive/archive_getdate.c b/libarchive/archive_getdate.c
index beb0cba..fe43ae8 100644
--- a/libarchive/archive_getdate.c
+++ b/libarchive/archive_getdate.c
@@ -691,7 +691,7 @@
 	time_t Hours, time_t Minutes, time_t Seconds,
 	time_t Timezone, enum DSTMODE DSTmode)
 {
-	static int DaysInMonth[12] = {
+	int DaysInMonth[12] = {
 		31, 0, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
 	};
 	time_t	Julian;