Shorten endian conversion method names

The consensus on #14917 was that the proposed names were too long.

src/libserialize/ebml.rs

@@ -183,7 +183,7 @@ pub mod reader {
 
         unsafe {
             let ptr = data.as_ptr().offset(start as int) as *u32;
-            let val = Int::from_big_endian(*ptr);
+            let val = Int::from_be(*ptr);
 
             let i = (val >> 28u) as uint;
             let (shift, mask) = SHIFT_MASK_TABLE[i];