Fix errors in how parsed time values were used

%u flag takes a value in the range of 1-7. However value needs to be
stored in tm.tm_wday between 0 and 6.
%y takes a two-digit year value. Subtracting 1900_i32 from it is not
needed.

src/libstd/time.rs

@@ -551,7 +551,7 @@ priv fn do_strptime(s: &str, format: &str) -> Result<Tm, ~str> {
             match match_digits(s, pos, 1u, false) {
               Some(item) => {
                 let (v, pos) = item;
-                tm.tm_wday = v;
+                tm.tm_wday = v-1_i32;
                 Ok(pos)
               }
               None => Err(~"Invalid day of week")
@@ -590,7 +590,7 @@ priv fn do_strptime(s: &str, format: &str) -> Result<Tm, ~str> {
             match match_digits(s, pos, 2u, false) {
               Some(item) => {
                 let (v, pos) = item;
-                tm.tm_year = v - 1900_i32;
+                tm.tm_year = v;
                 Ok(pos)
               }
               None => Err(~"Invalid year")