Remove reexports from core top level

[brson]

In core.rc the 'Reexported core operators' and 'Reexported types and traits' sections should not exist. These are part of the prelude module now.

[sammykim]

I take this. I will pull requests as soon as possible. But it seems there are another issue about this.
When I finish it, I will leave the comment about that issue with pull request.

[sammykim]

Removing ops::{Drop}, ops::{BitAnd, BitOr, BitXor}, path::WindowsPath, path::PosixPath, num::NumCast is OK.
but another operators and traits can't be removed.

I think prelude doens't work properly.

e.g ops::{Shl, Shr, Index};
error message :
/home/sammy.kim/rust/src/libstd/bigint.rs:102:0: 108:1 error: attempt to implement an unknown trait
/home/sammy.kim/rust/src/libstd/bigint.rs:102 impl Shl<uint, BigUint> for BigUint {
/home/sammy.kim/rust/src/libstd/bigint.rs:103 fn shl(&self, rhs: &uint) -> BigUint {
/home/sammy.kim/rust/src/libstd/bigint.rs:104 let n_unit = *rhs / BigDigit::bits;
/home/sammy.kim/rust/src/libstd/bigint.rs:105 let n_bits = *rhs % BigDigit::bits;
/home/sammy.kim/rust/src/libstd/bigint.rs:106 return self.shl_unit(n_unit).shl_bits(n_bits);
/home/sammy.kim/rust/src/libstd/bigint.rs:107 }
...
/home/sammy.kim/rust/src/libstd/bigint.rs:110:0: 116:1 error: attempt to implement an unknown trait
/home/sammy.kim/rust/src/libstd/bigint.rs:110 impl Shr<uint, BigUint> for BigUint {
/home/sammy.kim/rust/src/libstd/bigint.rs:111 fn shr(&self, rhs: &uint) -> BigUint {
/home/sammy.kim/rust/src/libstd/bigint.rs:112 let n_unit = *rhs / BigDigit::bits;
/home/sammy.kim/rust/src/libstd/bigint.rs:113 let n_bits = *rhs % BigDigit::bits;
/home/sammy.kim/rust/src/libstd/bigint.rs:114 return self.shr_unit(n_unit).shr_bits(n_bits);
/home/sammy.kim/rust/src/libstd/bigint.rs:115 }
...
/home/sammy.kim/rust/src/libstd/bigint.rs:618:0: 622:1 error: attempt to implement an unknown trait
/home/sammy.kim/rust/src/libstd/bigint.rs:618 impl Shl<uint, BigInt> for BigInt {
/home/sammy.kim/rust/src/libstd/bigint.rs:619 fn shl(&self, rhs: &uint) -> BigInt {
/home/sammy.kim/rust/src/libstd/bigint.rs:620 BigInt::from_biguint(self.sign, self.data << *rhs)
/home/sammy.kim/rust/src/libstd/bigint.rs:621 }
/home/sammy.kim/rust/src/libstd/bigint.rs:622 }
/home/sammy.kim/rust/src/libstd/bigint.rs:624:0: 628:1 error: attempt to implement an unknown trait
/home/sammy.kim/rust/src/libstd/bigint.rs:624 impl Shr<uint, BigInt> for BigInt {
/home/sammy.kim/rust/src/libstd/bigint.rs:625 fn shr(&self, rhs: &uint) -> BigInt {
/home/sammy.kim/rust/src/libstd/bigint.rs:626 BigInt::from_biguint(self.sign, self.data >> *rhs)
/home/sammy.kim/rust/src/libstd/bigint.rs:627 }
/home/sammy.kim/rust/src/libstd/bigint.rs:628 }
error: aborting due to 4 previous errors

Plz leave comment
Thanks.