big: Create type nat
Changed most of the functions in nat.go to methods on nat.
R=gri
CC=golang-dev
https://golang.org/cl/976041
diff --git a/src/pkg/big/int_test.go b/src/pkg/big/int_test.go
index 914a631..bb42f81 100644
--- a/src/pkg/big/int_test.go
+++ b/src/pkg/big/int_test.go
@@ -327,8 +327,8 @@
// See Knuth, Volume 2, section 4.3.1, exercise 21. This code exercises
// a code path which only triggers 1 in 10^{-19} cases.
- u := &Int{false, []Word{0, 0, 1 + 1<<(_W-1), _M ^ (1 << (_W - 1))}}
- v := &Int{false, []Word{5, 2 + 1<<(_W-1), 1 << (_W - 1)}}
+ u := &Int{false, nat{0, 0, 1 + 1<<(_W-1), _M ^ (1 << (_W - 1))}}
+ v := &Int{false, nat{5, 2 + 1<<(_W-1), 1 << (_W - 1)}}
r := new(Int)
q, r := new(Int).DivMod(u, v, r)
